Reaction: ATP + L-isoleucine + acetoacetyl-CoA = AMP + diphosphate + tenuazonic acid + CoA
Glossary: tenuazonic acid = (5S)-3-acetyl-5-[(2S)-butan-2-yl]-4-hydroxy-1,5-dihydro-2H-pyrrol-2-one
Other name(s): TAS1 (gene name)
Systematic name: L-isoleucine:acetoacetyl-CoA ligase (tenuazonic acid-forming)
Comments: This fungal enzyme, isolated from Magnaporthe oryzae, is an non-ribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) hybrid protein that consists of condensation (C), adenylation (A) and peptidyl-carrier protein (PCP) domains in the NRPS portion and a ketosynthase (KS) domain in the PKS portion. ATP is required for activation of isoleucine, which is then condensed with acetoacetyl-CoA. Cyclization and release from the enzyme are catalysed by the KS domain.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Yun, C.S., Motoyama, T. and Osada, H. Biosynthesis of the mycotoxin tenuazonic acid by a fungal NRPS-PKS hybrid enzyme. Nat Commun 6 (2015) 8758. [PMID: 26503170]