- Pseudomonas fluorescens Strain R124 Encodes Three Different MIO Enzymes
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A number of class I lyase-like enzymes, including aromatic ammonia-lyases and aromatic 2,3-aminomutases, contain the electrophilic 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) catalytic moiety. This study reveals that Pseudomonas fluorescens R124 strain isolated from a nutrient-limited cave encodes a histidine ammonia-lyase, a tyrosine/phenylalanine/histidine ammonia-lyase (XAL), and a phenylalanine 2,3-aminomutase (PAM), and demonstrates that an organism under nitrogen-limited conditions can develop novel nitrogen fixation and transformation pathways to enrich the possibility of nitrogen metabolism by gaining a PAM through horizontal gene transfer. The novel MIO enzymes are potential biocatalysts in the synthesis of enantiopure unnatural amino acids. The broad substrate acceptance and high thermal stability of PfXAL indicate that this enzyme is highly suitable for biocatalysis.
- Csuka, Pál,Juhász, Vivien,Kohári, Szabolcs,Filip, Alina,Varga, Andrea,Sátorhelyi, Péter,Bencze, László Csaba,Barton, Hazel,Paizs, Csaba,Poppe, László
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- Moderate UV Exposure Enhances Learning and Memory by Promoting a Novel Glutamate Biosynthetic Pathway in the Brain
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Sunlight exposure is known to affect mood, learning, and cognition. However, the molecular and cellular mechanisms remain elusive. Here, we show that moderate UV exposure elevated blood urocanic acid (UCA), which then crossed the blood-brain barrier. Single-cell mass spectrometry and isotopic labeling revealed a novel intra-neuronal metabolic pathway converting UCA to glutamate (GLU) after UV exposure. This UV-triggered GLU synthesis promoted its packaging into synaptic vesicles and its release at glutamatergic terminals in the motor cortex and hippocampus. Related behaviors, like rotarod learning and object recognition memory, were enhanced after UV exposure. All UV-induced metabolic, electrophysiological, and behavioral effects could be reproduced by the intravenous injection of UCA and diminished by the application of inhibitor or short hairpin RNA (shRNA) against urocanase, an enzyme critical for the conversion of UCA to GLU. These findings reveal a new GLU biosynthetic pathway, which could contribute to some of the sunlight-induced neurobehavioral changes. UV-induced upregulation of a small molecule feeds into an intraneuronal metabolic pathway for glutamate biosynthesis that can enhance learning and memory.
- Zhu, Hongying,Wang, Ning,Yao, Lei,Chen, Qi,Zhang, Ran,Qian, Junchao,Hou, Yiwen,Guo, Weiwei,Fan, Sijia,Liu, Siling,Zhao, Qiaoyun,Du, Feng,Zuo, Xin,Guo, Yujun,Xu, Yan,Li, Jiali,Xue, Tian,Zhong, Kai,Song, Xiaoyuan,Huang, Guangming,Xiong, Wei
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- 15N/14N position-specific isotopic analyses of polynitrogenous amino acids
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15N/14N isotope ratios are widely used to study processes and systems involving amino acids. Nitrogen isotope fractionation in biological processes occurs primarily at sites of bond-breaking and formation; the finest discrimination for "isotopic fingerprinting" and studies of isotopic fluxes is thus obtained at the position-specific level. While there are numerous reports of natural intramolecular carbon isotope variability, there are no literature reports of 15N/14N position-specific isotopic analysis (N-PSIA) of biologically relevant molecules. We report a methodology for high-precision N-PSIA of four polynitrogenous α-amino acids (asparagine, glutamine, lysine, histidine) and the first survey of natural intramolecular 15N/14N in these biomolecules. Selective liberation of N-atoms from multiple commercial standards of each parent amino acid was achieved by an appropriate enzymatic reaction or by acid hydrolysis. 15N/14N measurements were performed on N-ethoxycarbonyl ethyl ester derivatives of the parent amino acids and their analogues by gas chromatography combustion isotope ratio mass spectrometry, and the average precision for replicate injections was found to be SD(δ15N) = 0.3‰. Position-specific δ15N values of the parent amino acid were directly observed or indirectly calculated using mass balance. The average precision obtained for directly measured positions was SD(δ15N) = 0.2-0.4‰. The average precision for indirectly obtained positions was SD(δ15N) = 0.6-1.3‰ as a result of propagation of errors. Enrichment in the side chain-N with respect to the peptide-N was observed in nearly all of the amino acid sources, most notably in asparagine (average Δδside-peptide = +11‰), which may be indicative of its method of production. In some cases, it was possible to distinguish commercial sources by N-PSIA that could not be distinguished at the compound-specific level.
- Sacks, Gavin L.,Brenna, J. Thomas
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- Controlled release of mercury into aqueous L-(-) histidine solutions : Biological implications of electrochemical studies
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Controlled release of mercury into aqueous L-(-) histidine solutions is examined in this study. The first effect of mercury on histidine is mercuration to yield two derivatives both of which are paramagnetic and contain monomeric Hg+ ion. In one of the compounds, mercuration is at the imidazole nitrogen while in the other it is at the alaninyl side chain. These two organomercurials undergo intramolecular transformations independently to yield urocanic and glutamic acids respectively. The net effect is the mercury-assisted deamination and oxidation of L-histidine. Urocanic acid also reacts with mercury to yield predominantly a Hg+ compound. The significance of the results to biological systems is considered. Monomeric mercurous mercury appears to be a potential intermediate-in mercury toxification process. UV-vis, IR and EPR spectra of Hg+ compounds are discussed in the light of the results from cyclic voltammetry and dc and ac polarography.
- Renuka,Shakuntala,Srinivasan
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p. 596 - 605
(2007/10/03)
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- Sunscreen agents
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Hydroxy salts of formula: where M is zinc, copper or a mixture of the two and X denotes anions at least some of which display ultraviolet absorption over at least a portion of the wavelength range from 290 to 400 nanometers, their use as sunscreen agents and sunscreen compositions comprising them together with a cosmetically acceptable vehicle.
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- Sunscreen agents
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A sunscreen composition for application to human skin comprises an ultraviolet absorber which is introduced as an anion into a layered double hydroxide of the general formula where M is a divalent metal or lithium, N is a trivalent metal and X denotes anions present as an interlayer between layers of metal atoms joined through the OH groups. Such layered double hydroxides are, for this invention, suspended in a cosmetically acceptable vehicle.
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