Identification and functional characterisation of genes and corresponding enzymes involved in carnitine metabolism of Proteus sp.
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.
Engemann
Claudia
C
Pharmazie und Psychologie, Fakultät für Biowissenschaften, Institut für Biochemie, Universität Leipzig, Germany.
Elssner
Thomas
T
Pfeifer
Sven
S
Krumbholz
Carsten
C
Maier
Thomas
T
Kleber
Hans-Peter
HP
D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017920:Antiporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001622:Betaine / Q000031:analogs & derivatives* / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism*; D003001:Cloning, Molecular; D003066:Coenzyme A Ligases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry; D004746:Enoyl-CoA Hydratase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D010088:Oxidoreductases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011511:Proteus / Q000201:enzymology* / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D017920:Antiporters; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011994:Recombinant Proteins; C413607:crotonobetainyl-CoA; D001622:Betaine; C025237:crotonic acid betaine; D010088:Oxidoreductases; D000217:Acyltransferases; C060278:crotonobetainyl-CoA carnitine coenzyme A transferase; D004746:Enoyl-CoA Hydratase; D003066:Coenzyme A Ligases; D002331:Carnitine