title: The modified beta-ketoadipate pathway in Rhodococcus rhodochrous N75: enzymology of 3-methylmuconolactone metabolism.
abstract: Rhodococcus rhodochrous N75 is able to metabolize 4-methylcatechol via a modified beta-ketoadipate pathway. This organism has been shown to activate 3-methylmuconolactone by the addition of coenzyme A (CoA) prior to hydrolysis of the butenolide ring. A lactone-CoA synthetase is induced by growth of R. rhodochrous N75 on p-toluate as a sole source of carbon. The enzyme has been purified 221-fold by ammonium sulfate fractionation, hydrophobic chromatography, gel filtration, and anion-exchange chromatography. The enzyme, termed 3-methylmuconolactone-CoA synthetase, has a pH optimum of 8.0, a native Mr of 128,000, and a subunit Mr of 62,000, suggesting that the enzyme is homodimeric. The enzyme is very specific for its 3-methylmuconolactone substrate and displays little or no activity with other monoene and diene lactone analogues. Equimolar amounts of these lactone analogues brought about less than 30% (most brought about less than 15%) inhibition of the CoA synthetase reaction with its natural substrate.
authors.affiliation: Institute of Biotechnology, University of Cambridge, Cambridge CB2 1QT, United Kingdom.
authors.forename: C J
authors.initials: CJ
authors.lastname: Cha
authors.forename: R B
authors.initials: RB
authors.lastname: Cain
authors.forename: N C
authors.initials: NC
authors.lastname: Bruce
mesh_terms: D000272:Adipates / Q000378:metabolism*; D001426:Bacterial Proteins; D019748:Carbon-Carbon Double Bond Isomerases / Q000302:isolation & purification / Q000378:metabolism; D003066:Coenzyme A Ligases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D012240:Rhodococcus / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: C116618:3-methylmuconolactone; D000272:Adipates; D001426:Bacterial Proteins; D007783:Lactones; C027316:3-oxoadipic acid; D019748:Carbon-Carbon Double Bond Isomerases; C100087:muconolactone delta-isomerase; C116682:3-methylmuconolactone-CoA synthetase; D003066:Coenzyme A Ligases