Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Selenium occurs normally in living things as a highly specific component of certain enzymes and amino acid transfer nucleic acids (tRNAs). In bacteria, biosynthesis of essential selenoenzymes has been shown to be unaffected by wide variations in sulfur levels. The naturally occurring selenoenzymes so far identified from bacterial sources include glycine reductase, certain formate dehydrogenases, a hydrogenase, nicotinic acid hydroxylase, xanthine dehydrogenase and thiolase. The selenoenzyme, glutathione peroxidase, and three other selenoproteins of unknown function have been isolated from animals. In certain enzymes, e.g. glycine reductase, formate dehydrogenase, hydrogenase and glutathione peroxidase, the chemical form of selenium has been identified as selenocysteine. One enzyme, a bacterial thiolase, contains selenomethionine rather than selenocysteine. A labile, unidentified form of selenium is present in nicotinic acid hydroxylase, and by inference, xanthine dehydrogenase. The seleno-tRNAs serve as examples of a different type of biological macromolecule that is specifically modified with selenium. The major seleno-tRNAs in Clostridium sticklandii and Escherichia coli have been identified as glutamate and lysine isoaccepting species. The selenium-modified nucleoside is 5-methyl-aminomethyl-2-selenouridine (mnm5Se2U), which is the chemical analog of 5-methylaminomethyl-2-thiouridine, a previously identified minor base of E. coli tRNA2Glu. The seleno-tRNAGlu of C. sticklandii contains one gram atom of Se per mole of biologically active tRNA. Loss of Se from the modified nucleoside, mnm5Se2U, in this tRNA results in concomitant loss of glutamate charging activity suggesting that selenium is essential for interaction of the synthetase and its cognate tRNA.
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PMID:New biologic functions--selenium-dependent nucleic acids and proteins. 622 14

The genome of the green alga Chlamydomonas reinhardtii encodes two [FeFe]-hydrogenases, HydA1 and HydA2, and the hydrogenase-like protein HYD3. The unique combination of these proteins in one eukaryotic cell allows for direct comparison of their in vivo functions, which have not been established for HydA2 and HYD3. Using an artificial microRNA silencing method developed recently, the expression of HydA1, HydA2 and HYD3 was specifically down-regulated. Silencing of HydA1 resulted in 4-fold lower hydrogenase protein and activity under anaerobic conditions. In contrast, silencing of HydA2 or HYD3 did not affect hydrogen production. Cell lines with strongly (>90%) decreased HYD3 transcript levels grew more slowly than wild-type. The activity of aldehyde oxidase, a cytosolic Fe-S enzyme, was decreased in HYD3-knockdown lines, whereas Fe-S dependent activities in the chloroplast and mitochondria were unaffected. In addition, the HYD3-knockdown lines grew poorly on hypoxanthine, indicating impaired function of xanthine dehydrogenase, another cytosolic Fe-S enzyme. The expression levels of selected genes in response to hypoxia were unaltered upon HYD3 silencing. Together, our results clearly distinguish the cellular roles of HydA1 and HYD3, and indicate that HYD3, like its yeast and human homologues, has an evolutionary conserved role in the biogenesis or maintenance of cytosolic Fe-S proteins.
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PMID:RNA silencing of hydrogenase(-like) genes and investigation of their physiological roles in the green alga Chlamydomonas reinhardtii. 2072 41