- Observing 3-hydroxyanthranilate-3,4-dioxygenase in action through a crystalline lens
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The synthesis of quinolinic acid from tryptophan is a critical step in the de novo biosynthesis of nicotinamide adenine dinucleotide (NAD+) in mammals. Herein, the nonheme iron-based 3-hydroxyanthranilate-3,4-dioxygenase responsible for quinolinic acid production was studied by performing time-resolved in crystallo reactions monitored by UV-vis microspectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and X-ray crystallography. Seven catalytic intermediates were kinetically and structurally resolved in the crystalline state, and each accompanies protein conformational changes at the active site. Among them, a monooxygenated, seven-membered lactone intermediate as a monodentate ligand of the iron center at 1.59-? resolution was captured, which presumably corresponds to a substrate-based radical species observed by EPR using a slurry of small-sized single crystals. Other structural snapshots determined at around 2.0-? resolution include monodentate and subsequently bidentate coordinated substrate, superoxo, alkylperoxo, and two metal-bound enol tautomers of the unstable dioxygenase product. These results reveal a detailed stepwise O-atom transfer dioxygenase mechanism along with potential isomerization activity that fine-tunes product profiling and affects the production of quinolinic acid at a junction of the metabolic pathway.
- Wang, Yifan,Liu, Kathy Fange,Yang, Yu,Davis, Ian,Liu, Aimin
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- STRUCTURE AND SYNTHESIS OF ATALAPHYLLINE AND RELATED ALKALOIDS
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The structure of atalaphylline, (1) 1,3,5-trihydroxy-4-(γ,γ-dimethylallyl)acridone an alkaloid of Atalantia monophylla, was confirmed by oxidative degradation and by total synthesis.The synthesis involves the preparation of 1,3,5-trihydroxy-9-acridone followed by direct prenylation to give atalaphylline and a monoprenylated product. - Key Word Index: Atalantia monophylla; Rutaceae; alkaloid; atalaphylline; 1,3,5-trihydroxy-4-(γ,γ-dimethylallyl)acridone; synthesis.
- Bahar, M. H.,Shringarpure, J. D.,Kulkarni, G. H.,Sabata, B. K.
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- Crystal structure of the Homo sapiens kynureninase-3-hydroxyhippuric acid inhibitor complex: Insights into the molecular basis of kynureninase substrate specificity
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Homo sapiens kynureninase is a pyridoxal-5'-phosphate dependent enzyme that catalyzes the hydrolytic cleavage of 3-hydroxykynurenine to yield 3-hydroxyanthranilate and L-alanine as part of the tryptophan catabolic pathway leading to the de novo biosynthesis of NAD+. This pathway results in quinolinate, an excitotoxin that is an NMDA receptor agonist. High levels of quinolinate have been correlated with the etiology of neurodegenerative disorders such as AIDS-related dementia and Alzheimer's disease. We have synthesized a novel kynureninase inhibitor, 3-hydroxyhippurate, cocrystallized it with human kynureninase, and solved the atomic structure. On the basis of an analysis of the complex, we designed a series of His- 102, Ser-332, and Asn-333 mutants. The H102W/N333T and H102W/S332G/N333T mutants showed complete reversal of substrate specificity between 3-hydroxykynurenine and L-kynurenine, thus defining the primary residues contributing to substrate specificity in kynureninases.
- Lima, Santiago,Kumar, Sunil,Gawandi, Vijay,Momany, Cory,Phillips, Robert S.
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p. 389 - 396
(2009/10/01)
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- A comparative study on the inhibition of human and bacterial kynureninase by novel bicyclic kynurenine analogues
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A series of novel bicyclic analogues of kynurenine were synthesised as inhibitors of kynureninase. The trytophan-induced bacterial enzyme from Pseudomonas fluorescens were compared to the constitutive recombinant human enzyme expressed in a baculovirus/insect cell system, with regard to their inhibition by these compounds. All the compounds studied were found to be simple competitive, reversible inhibitors of kynureninase. It was found that altering the size of the second ring of the inhibitor affected the observed Ki values for both enzymes. The addition of an oxygen atom into the second ring had little effect on binding to the bacterial enzyme but gave a more potent inhibitor of human kynureninase. Of the compounds tested, a naphthyl analogue of desaminokynurenine was found to be the most potent inhibitor for both enzymes with Ki values of 5 and 22 μM for bacterial and human enzyme respectively. This report also describes an alternative system for the expression of recombinant human kynureninase which is more convenient for expression in mammalian cells and produces a relatively greater quantity of enzyme. Copyright
- Fitzgerald, Deirdre H.,Muirhead, Karen M.,Botting, Nigel P.
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p. 983 - 989
(2007/10/03)
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- Decomposition of Cinnabarinic Acid by Hydrogen Peroxide
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The hydrogen peroxide-induced decomposition of cinnabarinic acid 2 has been examined.Two major compounds were found to arise from the decomposition; 3-hydroxyanthranilic acid 1, and an isomeric mixture of two novel hemiketals.
- Manthey, Michael K.,Pyne, Stephen G.,Truscott, Roger J. W.
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p. 263 - 264
(2007/10/02)
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- New methods and reagents in organic synthesis. 92. A stereoselective synthesis of tilivalline and its analogs
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Tilivalline (1a), a metabolite from Klebsiella pneumoniae var. oxytoca, and its derivatives 1 have been efficiently and stereoselectively synthesized from diphenyl phosphorazidate, the 2-oxazoline 2, the L-proline derivatives 5, and indole; the key step is a Mannich type intramolecular cyclization accompanied with completely stereoselective introduction of indole. Furthermore, 11-substituted 5H- pyrrolo[2,1-c][1,4]benzodiazepin-5-ones (16) have been also synthesized from the acetal amide 9a and various nucleophiles by the use of this new Mannich type cyclization.
- Mori, Shigehiro,Ohno, Tomoyasu,Harada, Hiroshi,Aoyama, Toyohiko,Shioiri, Takayuki
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p. 5051 - 5070
(2007/10/02)
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- NEW METHOD AND REAGENTS IN ORGANIC SYNTHESIS. 65. A STEREOSELECTIVE SYNTHESIS OF TILIVALLINE
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Tilivalline (1), a metabolite from Klebsiella, has been efficiently and stereoselectively synthesized from diphenyl phosphorazidate (DPPA), the 2-oxazoline 2, the L-proline derivative 5, and indole; the key step is a Mannich type intramolecular cyclization accompanied with simultaneous and completely stereoselective introduction of indole.
- Mori, Shigehiro,Aoyama, Toyohiko,Shioiri, Takayuki
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p. 6111 - 6114
(2007/10/02)
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- Melanin Formation and Break Down of Indole under Udenfriend Condition
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Indol under biomimetic hydroxylation using Udenfriend reaction gives rise to malamin and other products.The results pose a question whether indole could be an alternative substrate for biomelanin.
- Roy, Shyamali,Chakraborty, A. K.,Chakraborty, D. P.
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p. 992 - 993
(2007/10/02)
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- Hydroformylation of olefins using azoxy-dentated ligands
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At a temperature in the range 100° C to 225° C the destructive dissociation of cobalt carbonyl compounds to cobalt metal and residue is inhibited by the action of one or more azoxy-dentated chelation ligands.
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