443892-10-2

Basic information

• Product Name: Dihydronicotinamide adenine dinucleotide
• Synonyms: 1,4-Dihydronicotinamide adenine dinucleotide; Adenosine 5'-(trihydrogen pyrophosphate), 5'-5'-ester with 1,4-dihydro-1beta-D-ribofuranosylnicotinamide; Codehydrase I, reduced; Codehydrogenase I, reduced; Coenzyme I, reduced; Cozymase I, reduced; DPNH; Dihydrocodehydrogenase I; Dihydrocozymase; Dihydronicotinamide mononucleotide; NADH2; Nicotinamide - adenine dinucleotide, reduced; Reduced codehydrogenase I; Reduced diphosphopyridine nucleotide; Reduced nicotinamide adenine diphosphate; beta-DPNH; beta-NADH; dihydronicotinamide-adenine dinucleotide; [5-(6-aminopurin-9-yl)-3,4-dihydroxy-tetrahydrofuran-2-yl]methyl [[5-(3-carbamoyl-4H-pyridin-1-yl)-3,4-dihydroxy-tetrahydrofuran-2-yl]methoxy-hydroxy-phosphoryl] hydrogen phosphate; [(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-dihydroxy-tetrahydrofuran-2-yl]methyl [[(2R,3S,4R,5R)-5-(3-carbamoylpyridin-1-ium-1-yl)-3,4-dihydroxy-tetrahydrofuran-2-yl]methoxy-hydroxy-phosphoryl] hydrogen phosphate; [(2R,3S,4R,5S)-5-(6-amino-7H-purin-8-yl)-3,4-dihydroxytetrahydrofuran-2-yl]
• CAS NO: 443892-10-2
• Molecular Formula: C₂₁H₂₉N₇O₁₄P₂
• Molecular Weight: 665.441
• EINECS: 200-393-0
• Mol File: 443892-10-2.mol
• Article Data: 77

Chemical Properties

• Boiling Point: 1081.765°C at 760 mmHg
• Flash Point: 608.029°C
• Density: 2.18g/cm³
• Vapor Pressure: 0mmHg at 25°C
• Refractive Index: 1.845
• CAS DataBase Reference: Dihydronicotinamide adenine dinucleotide(CAS DataBase Reference)
• NIST Chemistry Reference: Dihydronicotinamide adenine dinucleotide(443892-10-2)
• EPA Substance Registry System: Dihydronicotinamide adenine dinucleotide(443892-10-2)

Safety Data

• Hazardous Substances Data: 443892-10-2(Hazardous Substances Data)

Upstream product

• 59-30-3 folate 
• 56-86-0 L-glutamic acid 
• 865-05-4 nicotinamide adenine dinucleotide 
• 144509-68-2 α-ketoglutarate 
• 865-05-4 NAD+ 
• 53-84-9 NAD 
• 53-84-9 nicotinamide adenine dinucleotide 
• 64-17-5 ethanol 
• 100-51-6 benzyl alcohol 
• 56-81-5 glycerol 
• 149-61-1 (S)-malate dicarboxylate 
• 3884-47-7 dihydrolipoamide 
• 142-47-2 monosodium L-glutamate 
• 53-84-9 nicotiamide adenine dinucleotide 

Relevant articles and documents

N, O -Chelating quinoline-based half-sandwich organorhodium and -iridium complexes: Synthesis, antiplasmodial activity and preliminary evaluation as transfer hydrogenation catalysts for the reduction of NAD+

Two Rh(iii) and Ir(iii) half-sandwich quinoline-based complexes were synthesised and evaluated for their in vitro antiplasmodial activity against the chloroquine-sensitive NF54 and multi-drug resistant K1 strains of the human malaria parasite, Plasmodium falciparum. These half-sandwich organometallic complexes can also facilitate transfer hydrogenation, by converting β-nicotinamide adenine dinucleotide (NAD+) to its reduced form (NADH) in the presence of sodium formate. Co-administration of the iridium(iii) complex with sodium formate enhances the antiplasmodial activity in the chloroquine-resistant (K1) strain of Plasmodium falciparum, intimating that metal-mediated transfer hydrogenations can be achieved in malarial parasitic cells.

Significance of the 20-kDa subunit of heterodimeric 2-deoxy-scyllo-inosose synthase for the biosynthesis of butirosin antibiotics in Bacillus circulans

A gene (btrC2) encoding the 20-kDa subunit of 2-deoxy-scyllo-inosose (DOI) synthase, a key enzyme in the biosynthesis of 2-deoxystreptamine, was identified from the butirosin-producer Bacillus circulans by reverse genetics. The deduced amino acid sequence of BtrC2 closely resembled that of YaaE of B. subtilis, but the function of the latter has not been known to date. Instead, BtrC2 appeared to show sequence similarity to a certain extent with HisH of B. subtilis, an amidotransferase subunit of imidazole glycerol phosphate synthase. Disruption of btrC2 reduced the growth rate compared with the wild type, and simultaneously antibiotic producing activity was lost. Addition of NH4Cl to the medium complemented only the growth rate of the disruptant, and both the growth rate and antibiotic production were restored by addition of yeast extract. In addition, a heterologous co-expression system of btrC2 with btrC was constructed in Escherichia coli. The simultaneously over-expressed BtrC2 and BtrC constituted a heterodimer, the biochemical features of which resembled those of DOI synthase from B. circulans more than those of the recombinant homodimeric BtrC. Despite the similarity of BtrC2 to HisH the heterodimer showed neither aminotransfer nor amidotransfer activity for 2-deoxy-scyllo-inosose as a substrate. All the observations suggest that BtrC2 is involved not only in the secondary metabolism, but also in the primary metabolism in B. circulans. The function of BtrC2 in the butirosin biosynthesis appears to be indirect, and may be involved in stabilization of DOI synthase and in regulation of its enzyme activity.

Synthesis of 4-alkylpyrazoles as inhibitors of liver alcohol dehydrogenase

Theoretical studies by shape analysis of the molecular electrostatic potential on the van der Waals surfaces of a set of 4-alkylpyrazoles predicted 4-isopentyl derivative as a good inhibitor of liver alcohol dehydrogenase. Thus, the new 4-isopentyl and the already known 4-octylpyrazole have been prepared by a novel route. The isopentyl derivative has been tested as inhibitor of horse liver alcohol dehydrogenase giving the result predicted by the theoretical studies.

NAD+-dependent (S)-specific secondary alcohol dehydrogenase involved in stereoinversion of 3-pentyn-2-ol catalyzed by Nocardia fusca AKU 2123

An NAD+-dependent alcohol dehydrogenase was purified to homogeneity from Nocardia fusca AKU 2123. The enzyme catalyzed (S)-specific oxidation of 3-pentyn-2-ol (PYOH), i.e., part of the stereoinversion reaction for the production of (R)-PYOH, which is a valuable chiral building block for pharmaceuticals, from the racemate. The enzyme used a broad variety of secondary alcohols including alkyl alcohols, alkenyl alcohols, acetylenic alcohols, and aromatic alcohols as substrates. The oxidation was (S)-isomer specific in every case. The Km and Vmax for (S)-PYOH and (S)-2-hexanol oxidation were 1.6 mM and 53 μmol/min/mg, and 0.33 mM and 130/μmol/min/mg, respectively. The enzyme also catalyzed stereoselective reduction of carbonyl compounds. (S)-2-Hexanol and ethyl (R)-4-chloro-3-hydroxybutanoate in high optical purity were produced from 2-hexanone and ethyl 4-chloro-3-oxobutanoate by the purified enzyme, respectively. The Km and Vmax for 2-hexanone reduction were 2.5 mM and 260 μmol/min/mg. The enzyme has a relative molecular mass of 150,000 and consists of four identical subunits. The NH2-terminal amino acid sequence of the enzyme shows similarity with those of the carbonyl reductase from Rhodococcus erythropolis and phenylacetaldehyde reductase from Corynebacterium sp.

Coenzyme analogs: Excellent substitutes (not poor imitations) for electrochemical regeneration

For the first time, employment of nicotinamide coenzyme NAD analogs has overcome the limitations of NAD in electrochemical regeneration. It has been shown that NAD analogs, APAD and PAAD, were electrochemically reduced more efficiently than original NAD and that the stability of their reduced products was also much higher than NADH.

On the nature of mutual inactivation between [Cp*Rh(bpy)(H2O)]2+ and enzymes - analysis and potential remedies

Pentamethylcyclopentadienyl rhodium bipyridine ([Cp*Rh(bpy)(H2O)]2+) is a versatile catalyst to promote biocatalytic redox reactions. However, its major drawback lies in the mutual inactivation of [Cp*Rh(bpy)(H2O)]2+ and the biocatalyst. This interaction was investigated using the alcohol dehydrogenase from Thermus sp. ATN1 (TADH) as model enzyme. TADH binds 4equiv. of [Cp*Rh(bpy)(H2O)]2+ without detectable decrease in catalytic activity and stability. Higher molar ratios lead to time-, temperature-, and concentration-dependent inactivation of the enzyme suggesting [Cp*Rh(bpy)(H2O)]2+ to function as an 'unfolding catalyst'. This detrimental activity can be circumvented using strongly coordinating buffers (e.g. (NH4)2SO4) while preserving its activity as NAD(P)H regeneration catalyst under electrochemical reaction conditions.

A highly efficient covalent organic framework film photocatalyst for selective solar fuel production from CO2

Two-dimensional covalent organic frameworks (2D COFs) are a class of crystalline polymers with a design controllable platform that may be developed into a new type of metal-free photocatalyst. The exploration of new frameworks is, however, critical for further progress in this emerging field. To realize their full potential in practical light harvesting applications, the fabrication of a film type photocatalyst is equally essential. Here, we report the successful development of a triazine based covalent organic framework (2D CTF) as an inexpensive and highly efficient visible light active flexible film photocatalyst for solar fuel production from CO2. For this research work, the condensation polymerization between cyanuric chloride and perylene diimide has been exploited for the first time as a new synthetic approach to the construction of 2D CTFs. The visible light-harvesting capacity, suitable band gap and highly ordered π electron channels contribute to the excellent performance of the film photocatalyst. The current study is a benchmark example of COF based photocatalysts for solar fuel production from CO2 and is expected to trigger further interest in potential solar energy conversion applications such as wearable devices.

Enhanced reactivity of Lys182 explains the limited efficacy of biogenic amines in preventing the inactivation of glucose-6-phosphate dehydrogenase by methylglyoxal

This study examines the inactivation of the enzyme glucose 6-phosphate dehydrogenase (G6PD) by methylglyoxal (MG) and the eventual protection exerted by endogenous amines. To determine the protective effect of amines, the rate constant of the reaction of MG with the amino group of N-α-acetyl-lysine, carnosine, spermine and spermidine was measured at pH 7.4, and the behavior of endogenous amines was analyzed on the basis of quantum chemical reactivity descriptors. A 63% reduction in the enzyme activity was found upon incubation of G6PD with MG at pH 7.4. The inactivation of G6PD was even larger when the pH was increased to 9.4, revealing a weak protective effect by the amines. The results suggest that some basic residues of G6PD exhibit an anomalous reactivity, which likely reflects a shift in the standard pKa value due to the local environment in the enzyme. Under the experimental conditions used in the assays, this hypothesis was corroborated by mass spectrometry analysis, which points out that modification of Lys182 in the binding site is responsible for the inactivation of G6PD by MG. These results emphasize the need to search for more effective antiglycating agents, which can compete with basic amino acid residues possessing enhanced reactivity in proteins.

G-C3N4α-Fe2O3/C Photocatalysts: Synergistically Intensified Charge Generation and Charge Transfer for NADH Regeneration

Graphitic carbon nitride (g-C3N4) is an emergent metal-free photocatalyst because of its band position, natural abundance, and facile preparation. Synergetic intensification of charge generation and charge transfer of g-C3N4 to increase solar-to-chemical efficiency remains a hot yet challenging issue. Herein, a nanoshell with two moieties of α-Fe2O3 and carbon (C) is in situ formed on the surface of a g-C3N4 core through calcination of Fe3+/polyphenol-coated melamine, thus acquiring g-C3N4α-Fe2O3/C coreshell photocatalysts. The α-Fe2O3 moiety acts as an additional photosensitizer, offering more photogenerated electrons, whereas the C moiety bridges a "highway" to facilitate the electron transfer either from α-Fe2O3 moiety to g-C3N4 or from g-C3N4 to C moiety. By tuning the proportion of these two moieties in the nanoshell, a photocurrent density of 3.26 times higher than pristine g-C3N4 is obtained. When utilized for photocatalytic regeneration of reduced nicotinamide adenine dinucleotide (NADH, a dominant cofactor in biohydrogenation reaction), g-C3N4α-Fe2O3/C exhibits an equilibrium NADH yield of 76.3% with an initial reaction rate (r) of 7.7 mmol h-1 g-1, among the highest r for photocatalytic NADH regeneration ever reported. Manipulating the coupling between charge generation and charge transfer may offer a facile, generic strategy to improve the catalytic efficiency of a broad range of photocatalysts other than g-C3N4.

EFFICIENT INDIRECT ELECTROCHEMICAL IN-SITU REGENERATION OF NADH: ELECTROCHEMICALLY DRIVEN ENZYMATIC REDUCTION OF PYRUVATE CATALYZED BY D-LDH

Using Cl (1) as redox catalyst for the continous NADH regeneration it was possible to perform an electrochemically driven enzymatic reduction of pyruvate to D-lactate catalyzed by D-LDH at a rate of 5 turnovers per hour.This is by a factor of 20 faster than the best results obtained until now.Current yields of 50 to 70 percent may be obtained.

Aldehyde dehydrogenase 1B1: Molecular cloning and characterization of a novel mitochondrial acetaldehyde-metabolizing enzyme

Ethanol-induced damage is largely attributed to its toxic metabolite, acetaldehyde. Clearance of acetaldehyde is achieved by its oxidation, primarily catalyzed by the mitochondrial class II aldehyde dehydrogenase (ALDH2). ALDH1B1 is another mitochondrial aldehyde dehydrogenase (ALDH) that shares 75% peptide sequence homology with ALDH2. Recent population studies in whites suggest a role for ALDH1B1 in ethanol metabolism. However, to date, no formal documentation of the biochemical properties of ALDH1B1 has been forthcoming. In this current study, we cloned and expressed human recombinant ALDH1B1 in Sf9 insect cells. The resultant enzyme was purified by affinity chromatography to homogeneity. The kinetic properties of purified human ALDH1B1 were assessed using a wide range of aldehyde substrates. Human ALDH1B1 had an exclusive preference for NAD + as the cofactor and was catalytically active toward short- and medium-chain aliphatic aldehydes, aromatic aldehydes, and the products of lipid peroxidation, 4-hydroxynonenal and malondialdehyde. Most importantly, human ALDH1B1 exhibited an apparent Km of 55 μM for acetaldehyde, making it the second low Km ALDH for metabolism of this substrate. The dehydrogenase activity of ALDH1B1 was sensitive to disulfiram inhibition, a feature also shared with ALDH2. The tissue distribution of ALDH1B1 in C57BL/6J mice and humans was examined by quantitative polymerase chain reaction, Western blotting, and immunohistochemical analysis. The highest expression occurred in the liver, followed by the intestinal tract, implying a potential physiological role for ALDH1B1 in these tissues. The current study is the first report on the expression, purification, and biochemical characterization of human ALDH1B1 protein. Copyright

The functions of key residues in the inhibitor, substrate and cofactor sites of human 3β-hydroxysteroid dehydrogenase type 1 are validated by mutagenesis

In postmenopausal women, human 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD1) is a critical enzyme in the conversion of DHEA to estradiol in breast tumors, while 3β-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland. The goals of this project are to determine if Arg195 in 3β-HSD1 vs. Pro195 in 3β-HSD2 in the substrate/inhibitor binding site is a critical structural difference responsible for the higher affinity of 3β-HSD1 for inhibitor and substrate steroids compared to 3β-HSD2 and whether Asp61, Glu192 and Thr8 are fingerprint residues for cofactor and substrate binding using site-directed mutagenesis. The R195P-1 mutant of 3β-HSD1 and the P195R-2 mutant of 3β-HSD2 have been created, expressed, purified and characterized kinetically. Dixon analyses of the inhibition of the R195P-1 mutant, P195R-2 mutant, wild-type 3β-HSD1 and wild-type 3β-HSD2 by trilostane has produced kinetic profiles that show inhibition of 3β-HSD1 by trilostane (Ki=0.10μM, competitive) with a 16-fold lower Ki and different mode than measured for 3β-HSD2 (Ki=1.60μM, noncompetitive). The R195P-1 mutation shifts the high-affinity, competitive inhibition profile of 3β-HSD1 to a low-affinity (trilostane Ki=2.56μM), noncompetitive inhibition profile similar to that of 3β-HSD2 containing Pro195. The P195R-2 mutation shifts the low-affinity, noncompetitive inhibition profile of 3β-HSD2 to a high-affinity (trilostane Ki=0.19μM), competitive inhibition profile similar to that of 3β-HSD1 containing Arg195. Michaelis-Menten kinetics for DHEA, 16β-hydroxy-DHEA and 16α-hydroxy-DHEA substrate utilization by the R195P-1 and P195R-2 enzymes provide further validation for higher affinity binding due to Arg195 in 3β-HSD1. Comparisons of the Michaelis-Menten values of cofactor and substrate for the targeted mutants of 3β-HSD1 (D61N, D61V, E192A, T8A) clarify the functions of these residues as well.

Selective Usage of Isozymes for Stress Response

Isozymes are enzymes with similar sequences that catalyze the same reaction in a given species. In Saccharomyces cerevisiae, most isozymes have major isoforms with high expression levels and minor isoforms with little expression under normal growth conditions. In a proteomic study aimed at identifying yeast protein regulated by rapamycin, we found an interesting phenomenon, that, for several metabolic enzymes, the major isozymes are downregulated while the minor isozymes are upregulated. Through enzymological and biochemical studies, we demonstrate that a rapamycin-upregulated enolase isozyme (ENO1) favors gluconeogenesis and a rapamycin-upregulated alcohol dehydrogenase isozyme (ALD4) promotes the reduction of NAD+ to NADH (instead of NADP+ to NADPH). Gene deletion study in yeast showed that the ENO1 and ALD4 are important for yeast survival under less-favorable growth conditions. Therefore, our study highlights the different metabolic needs of cells under different conditions and how nature chooses different isozymes to fit the metabolic needs.

Plasmonic substrates comprising gold nanostars efficiently regenerate cofactor molecules

The light harvesting capacity of plasmonic nanoparticles is a fundamental feature for catalysing chemical reactions close to their surface. The efficiency of the photochemical processes depends not only on the geometrical aspects on a single particle level but also on the complexity of the multiparticle architectures. Although, the effect of the particle geometry is progressively understood in the relevant photochemical processes (water splitting and hydrogen evolution), there are experimental and theoretical needs for understanding the role of the shape in the multiparticle systems in the photocatalytic processes. Here we have shown that macroscopic plasmonic substrates comprising gold nanostars exhibit better efficiencies than nanorods or cubes in the photoregeneration of cofactor molecules. We performed photochemical and photoelectrochemical measurements, supported by theoretical simulations, showing that the unique geometry of nanostars-radially distributed spikes-contributes to stronger light absorption by the plasmonic film containing that type of nanoparticles.

Discrimination of aliphatic substrates by a single Amino acid substitution in bacillus and bacillus shaericus phenylalanine dehydrogenases

Replacement of glycine by serine at positions 123 and 124 of phenylalanine dehydrogenases from Bacillus badius and Bacillus sphaericus respectively strikingly decreased enzyme activity toward aromatic amino acids and resulted in an elevation of relative activity toward aliphatic amino acids. The mutant from B. badius preferentially dehydrogenated branched-chain amino acids, while that from B. sphaericus acted on amino acids with straight-chain amino acids.

Efficient catalytic interconversion between NADH and NAD+ accompanied by generation and consumption of hydrogen with a water-soluble iridium complex at ambient pressure and temperature

Regioselective hydrogenation of the oxidized form of β-nicotinamide adenine dinucleotide (NAD+) to the reduced form (NADH) with hydrogen (H2) has successfully been achieved in the presence of a catalytic amount of a [C,N] cyclometalated organoiridium complex [IrIII(Cp)(4- (1H-pyrazol-1-yl-κN2)benzoic acid-κC3)(H 2O)]2 SO4 [1]2·SO4 under an atmospheric pressure of H2 at room temperature in weakly basic water. The structure of the corresponding benzoate complex Ir III(Cp)(4-(1H-pyrazol-1-yl-κN2)-benzoate- κC3)(H2O) 2 has been revealed by X-ray single-crystal structure analysis. The corresponding iridium hydride complex formed under an atmospheric pressure of H2 undergoes the 1,4-selective hydrogenation of NAD+ to form 1,4-NADH. On the other hand, in weakly acidic water the complex 1 was found to catalyze the hydrogen evolution from NADH to produce NAD+ without photoirradiation at room temperature. NAD+ exhibited an inhibitory behavior in both catalytic hydrogenation of NAD+ with H2 and H2 evolution from NADH due to the binding of NAD+ to the catalyst. The overall catalytic mechanism of interconversion between NADH and NAD+ accompanied by generation and consumption of H2 was revealed on the basis of the kinetic analysis and detection of the catalytic intermediates.

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NAD-malic enzymes of Arabidopsis thaliana display distinct kinetic mechanisms that support differences in physiological control

The Arabidopsis thaliana genome contains two genes encoding NAD-MEs [NAD-dependent malic enzymes; NAD-ME1 (TAIR accession number At4G13560) and NAD-ME2 (TAIR accession number At4G00570)]. The encoded proteins are localized to mitochondria and assemble as homo- and hetero- dimers in vitro and in vivo. In the present work, the kinetic mechanisms of NAD-ME1 and -ME2 homodimers and NAD-MEH (NAD-ME heterodimer) were studied as an approach to understand the contribution of these enzymes to plant physiology. Product-inhibition and substrate-analogue analyses indicated that NAD-ME2 follows a sequential ordered Bi-Ter mechanism, NAD being the leading substrate followed by L-malate. On the other hand, NAD-ME1 and NAD-MEH can bind both substrates randomly. However, NAD-ME1 shows a preferred route that involves the addition ofNADfirst.As a consequence of the kinetic mechanism, NAD-ME1 showed a partial inhibition by L-malate at low NAD concentrations. The analysis of a protein chimaeric forNAD-ME1 and -ME2 indicated that the first 176 amino acids are associated with the differences observed in the kinetic mechanisms of the enzymes. Furthermore, NAD-ME1, -ME2 and -MEH catalyse the reverse reaction (pyruvate reductive carboxylation) with very low catalytic activity, supporting the notion that these isoforms act only in L-malate oxidation in plant mitochondria. The different kinetic mechanism of each NAD-ME entity suggests that, for a metabolic condition in which the mitochondrial NAD level is low and the L-malate level is high, the activity of NAD-ME2 and/or -MEH would be preferred over that of NAD-ME1. The Authors.

Emissive Synthetic Cofactors: A Highly Responsive NAD+ Analogue Reveals Biomolecular Recognition Features

Apart from its vital function as a redox cofactor, nicotinamide adenine dinucleotide (NAD+) has emerged as a crucial substrate for NAD+-consuming enzymes, including poly(ADP-ribosyl)transferase 1 (PARP1) and CD38/CD157. Their association with severe diseases, such as cancer, Alzheimer's disease, and depressions, necessitates the development of new analytical tools based on traceable NAD+ surrogates. Here, the synthesis, photophysics and biochemical utilization of an emissive, thieno[3,4-d]pyrimidine-based NAD+ surrogate, termed NthAD+, are described. Its preparation was accomplished by enzymatic conversion of synthetic thATP by nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1). The new NAD+ analogue possesses useful photophysical features including redshifted absorption and emission maxima as well as a relatively high quantum yield. Serving as a versatile substrate, NthAD+ was reduced by alcohol dehydrogenase (ADH) to NthADH and afforded thADP-ribose (thADPr) upon hydrolysis by NAD+-nucleosidase (NADase). Furthermore, NthAD+ was engaged in cholera toxin A (CTA)-catalyzed mono(thADP-ribosyl)ation, but was found incapable in promoting PARP1-mediated poly(thADP-ribosyl)ation. Due to its high photophysical responsiveness, NthAD+ is suited for spectroscopic real-time monitoring. Intriguingly, and as an N7-lacking NAD+ surrogate, the thieno-based cofactor showed reduced compatibility (i.e., functional similarity compared to native NAD+) relative to its isothiazolo-based analogue. The distinct tolerance, displayed by diverse NAD+ producing and consuming enzymes, suggests unique biological recognition features and dependency on the purine N7 moiety, which is found to be of importance, if not essential, for PARP1-mediated reactions.

Engineering Olefin-Linked Covalent Organic Frameworks for Photoenzymatic Reduction of CO2

It is of profound significance concerning the global energy and environmental crisis to develop new techniques that can reduce and convert CO2. To address this challenge, we built a new type of artificial photoenzymatic system for CO2 reduction, using a rationally designed mesoporous olefin-linked covalent organic framework (COF) as the porous solid carrier for co-immobilizing formate dehydrogenase (FDH) and Rh-based electron mediator. By adjusting the incorporating content of the Rh electronic mediator, which facilitates the regeneration of nicotinamide cofactor (NADH) from NAD+, the apparent quantum yield can reach as high as 9.17±0.44 %, surpassing all reported NADH-regenerated photocatalysts constructed by crystalline framework materials. Finally, the assembled photocatalyst–enzyme coupled system can selectively convert CO2 to formic acid with high efficiency and good reusability. This work demonstrates the first example using COFs to immobilize enzymes for artificial photosynthesis systems that utilize solar energy to produce value-added chemicals.

A highly active Cp*Ir complex with an anionic N,N-donor chelate ligand catalyzes the robust regeneration of NADH under physiological conditions

A highly active [N^N?] iridium complex [Cp*Ir(pba)Cl] (3, Cp* = pentamethylcyclopentadiene, pba = 4-(picolinamido)benzoic acid) has been obtained with an anionic ligand, which exhibited the most robust performance for cofactor NADH regeneration in physiological conditions with HCOONa as the hydrogen source. The structure of complex3was revealed by X-ray single-crystal structure analysis. The turnover frequency (TOF) of complex3in the regeneration of NADH is 7825 h?1, which is about 22.7 times and 178 times higher than that of the C?^N type complex2(345 h?1) and N^N complex1(44 h?1) at 37 °C, respectively. The high activity of complex3seems to be critically affected by the negatively charged N?of the amide chelating ligand, which could promote the reaction rate of Ir-Cl conversion to Ir-H2O. Furthermore, complex3shows good biocompatibility for various biomolecules except SH-compounds (such as reduced glutathione (GSH)). When combined with NADH-dependent enzymes (KRED-101), the complex3-based NADH-regeneration catalytic system shows stable chemoenzymatical coordinate catalytic activity for reducing acetophenone to the corresponding alcohol with high enantioselectivity.