IUBMB Enzyme Nomenclature


Accepted name: L-carnitine CoA-transferase

Reaction: (1) (E)-4-(trimethylammonio)but-2-enoyl-CoA + L-carnitine = (E)-4-(trimethylammonio)but-2-enoate + L-carnitinyl-CoA
(2) 4-trimethylammoniobutanoyl-CoA + L-carnitine = 4-trimethylammoniobutanoate + L-carnitinyl-CoA

Glossary: L-carnitine = (3R)-3-hydroxy-4-(trimethylammonio)butanoate
(E)-4-(trimethylammonio)but-2-enoate = crotonobetaine
4-trimethylammoniobutanoate = γ-butyrobetaine

Other name(s): CaiB; crotonobetainyl/γ-butyrobetainyl-CoA:carnitine CoA-transferase

Systematic name: (E)-4-(trimethylammonio)but-2-enoyl-CoA:L-carnitine CoA-transferase

Comments: The enzyme is found in gammaproteobacteria such as Proteus sp. and Escherichia coli. It has similar activity with both substrates.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:


1. Engemann, C., Elssner, T. and Kleber, H.P. Biotransformation of crotonobetaine to L-(–)-carnitine in Proteus sp. Arch. Microbiol. 175 (2001) 353-359. [PMID: 11409545]

2. Elssner, T., Engemann, C., Baumgart, K. and Kleber, H.P. Involvement of coenzyme A esters and two new enzymes, an enoyl-CoA hydratase and a CoA-transferase, in the hydration of crotonobetaine to L-carnitine by Escherichia coli. Biochemistry 40 (2001) 11140-11148. [PMID: 11551212]

3. Stenmark, P., Gurmu, D. and Nordlund, P. Crystal structure of CaiB, a type-III CoA transferase in carnitine metabolism. Biochemistry 43 (2004) 13996-14003. [PMID: 15518548]

4. Engemann, C., Elssner, T., Pfeifer, S., Krumbholz, C., Maier, T. and Kleber, H.P. Identification and functional characterisation of genes and corresponding enzymes involved in carnitine metabolism of Proteus sp. Arch. Microbiol. 183 (2005) 176-189. [PMID: 15731894]

5. Rangarajan, E.S., Li, Y., Iannuzzi, P., Cygler, M. and Matte, A. Crystal structure of Escherichia coli crotonobetainyl-CoA: carnitine CoA-transferase (CaiB) and its complexes with CoA and carnitinyl-CoA. Biochemistry 44 (2005) 5728-5738. [PMID: 15823031]

[EC created 2014]

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