Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Crotonobetaine reductase from Escherichia coli 044 K74 is an inducible enzyme detectable only in cells grown anaerobically in the presence of L(-)-carnitine or crotonobetaine as inducers. Enzyme activity was not detected in cells cultivated in the presence of inducer plus glucose, nitrate, gamma-butyrobetaine or oxygen, respectively. Fumarate caused an additional stimulation of growth and an increased expression of crotonobetaine reductase. The reaction product, gamma-butyrobetaine, was identified by autoradiography. Crotonobetaine reductase is localized in the cytoplasm, and has been characterized with respect to pH (pH 7.8) and temperature optimum (40-45 degrees C). The Km value for crotonobetaine was determined to be 1.1 x 10(-2M). gamma-Butyrobetaine, D(+)-carnitine and choline are inhibitors of crotonobetaine reduction. For gamma-butyrobetaine (Ki = 3 x 10(-5M)) a competitive inhibition type was determined. Various properties suggest that crotonobetaine reductase is different from other reductases of anaerobic respiration.
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PMID:Crotonobetaine reductase from Escherichia coli--a new inducible enzyme of anaerobic metabolization of L(-)-carnitine. 806 Jan 25

L-(-)-Carnitine is a ubiquitously occurring substance, essential for the transport of long-chain fatty acids through the inner mitochondrial membrane. Bacteria are able to metabolize this trimethylammonium compound in three different ways. Some, especially Pseudomonas species, assimilate L-(-)-carnitine as sole source of carbon and nitrogen. The first catabolic step is catalysed by the L-(-)-carnitine dehydrogenase. Others, for instance, Acinetobacter species, degrade only the carbon backbone, with formation of trimethylamine. Finally, various members of the Enterobacteriaceae are able to convert carnitine, via crotonobetaine, to gamma-butyrobetaine in the presence of C and N sources and under anaerobic conditions. This two-step pathway, including a L-(-)-carnitine dehydratase and the crotonobetaine reductase, was demonstrated in Escherichia coli. The DNA sequence encompassing the cai genes of E. coli, which encode the carnitine pathway, has been determined. Some bacteria are also able to metabolize the non-physiological D-(+)-carnitine, which results as a waste product in some chemical procedures for L-(-)-carnitine production based on the resolution of racemic carnitine.
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PMID:Bacterial carnitine metabolism. 903 56

Different Enterobacteriaceae, such as Escherichia coli, Proteus vulgaris and Proteus mirabilis, are able to convert L(-)-carnitine, via crotonobetaine, into gamma-butyrobetaine in the presence of carbon and nitrogen sources under aerobic conditions. Intermediates of L(-)-carnitine metabolism (crotonobetaine, gamma-butyrobetaine) could be detected by thin-layer chromatography. In parallel, L(-)-carnitine dehydratase, carnitine racemasing system and crotonobetaine reductase activities were determined enzymatically. Monoclonal antibodies against purified CaiB and CaiA from E. coli O44K74 were used to screen cell-free extracts of different Enterobacteriaceae (E. coli ATCC 25922, P. vulgaris, P. mirabilis, Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae) grown under aerobic conditions in the presence of L(-)-carnitine.
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PMID:Metabolism of L(-)-carnitine by Enterobacteriaceae under aerobic conditions. 1033 22

A still unknown low-molecular-mass cofactor essential for the activity of carnitine-metabolizing enzymes (e.g., L-carnitine dehydratase, crotonobetaine reductase) from E. coli has been purified to homogeneity from a cell-free extract of E. coli O44K74. The purity of the cofactor was confirmed by HPLC analysis. Biosynthesis of the unknown compound was only observed when bacteria were cultivated anaerobically in the presence of L-carnitine or crotonobetaine. The determined properties, together with results obtained from UV-visible, (1)H NMR, and mass spectrometry, indicate that the compound in question is a new CoA derivative. The esterified compound was suggested to be gamma-butyrobetaine-a metabolite of carnitine metabolism of E. coli. Proof of structure was performed by chemical synthesis. Besides gamma-butyrobetainyl-CoA, a second new CoA derivative, crotonobetainyl-CoA, was also chemically synthesized. Both CoA derivatives were purified and their structures confirmed using NMR and mass spectrometry. Comparisons of structural data and of the chemical properties of gamma-butyrobetainyl-CoA, crotonobetainyl-CoA, and the isolated cofactor verified that the unknown compound is gamma-butyrobetainyl-CoA. The physical and chemical properties of gamma-butyrobetainyl-CoA and crotonobetainyl-CoA are similar to known CoA derivatives.
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PMID:Isolation, identification, and synthesis of gamma-butyrobetainyl-CoA and crotonobetainyl-CoA, compounds involved in carnitine metabolism of E. coli. 1097 61

Proteus sp. is able to catalyse the reversible transformation of crotonobetaine into L(-)-carnitine during aerobic growth. Contrary to other Enterobacteriaceae no reduction of crotonobetaine into gamma-butyrobetaine could be detected in the culture supernatants. Activities of L(-)-carnitine dehydratase, carnitine racemasing system and crotonobetaine reductase could be determined enzymatically in cell-free extracts of Proteus sp. Small amounts of gamma-butyrobetaine were found in cell-free extracts, indicating that it accumulates in the cell and inhibits the crotonobetaine reductase. Crotonobetaine and L(-)-carnitine were able to induce enzymes of carnitine metabolism. gamma-Butyrobetaine and glucose repress carnitine metabolism in Proteus sp. Other betaines are neither inducers nor repressors. Monoclonal antibodies against purified CaiA from Escherichia coli O44K74 recognise an analogous protein in cell-free extract of Proteus sp. No cross-reactivity could be detected with monoclonal antibodies against purified CaiB and CaiD from E. coli O44K74.
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PMID:Epigenetic regulation of carnitine metabolising enzymes in Proteus sp. under aerobic conditions. 1125 39

Enzymes involved in carnitine metabolism of Proteus sp. are encoded by the cai genes organised as the caiTABCDEF operon. The complete operon could be sequenced from the genomic DNA of Proteus sp. Amino acid sequence similarities and/or enzymatic analysis confirmed the function assigned to each protein involved in carnitine metabolism. CaiT was suggested to be an integral membrane protein responsible for the transport of betaines. The caiA gene product was shown to be a crotonobetainyl-CoA reductase catalysing the irreversible reduction of crotonobetainyl-CoA to gamma-butyrobetainyl-CoA. CaiB and CaiD were identified to be the two components of the crotonobetaine hydrating system, already described. CaiB and caiD were cloned and expressed in Escherichia coli. After purification of both proteins, their individual enzymatic functions were solved. CaiB acts as betainyl-CoA transferase specific for carnitine, crotonobetaine, gamma-butyrobetaine and its CoA derivatives. Transferase reaction proceeds, following a sequential bisubstrate mechanism. CaiD was identified to be a crotonobetainyl-CoA hydratase belonging to the crotononase superfamily. Because of amino acid sequence similarities, CaiC was suggested to be a betainyl-CoA ligase. Taken together, these results show that the metabolism of carnitine and crotonobetaine in Proteus sp. proceeds at the CoA level.
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PMID:Identification and functional characterisation of genes and corresponding enzymes involved in carnitine metabolism of Proteus sp. 1573 94