title: Deacetoxycephalosporin C synthase isozymes exhibit diverse catalytic activity and substrate specificity.
abstract: The biosynthesis of cephalosporins involving a thiozolidine ring expansion is catalyzed by deacetoxycephalosporin C synthase (DAOCS). In this study, three DAOCS isozymes were cloned and expressed as active enzymes together with Streptomyces jumonjinensis DAOCS that was newly isolated and partially characterized. The enzymes showed excellent substrate conversion for penicillin G, phenethicillin, ampicillin and carbenicillin, but they were less effective in the ring expansion of penicillin V, amoxicillin and metampicillin. Streptomyces clavuligerus DAOCS was the most active among the recombinant enzymes. The results also showed that truncation of 20 amino acids at the C-terminus of the Acremonium chrysogenum deacetoxy/deacetylcephalosporin C synthase polypeptide did not affect penicillin ring expansion.
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, 5 Science Drive 2, 117597, Singapore, Singapore.
authors.forename: Hong Soon
authors.initials: HS
authors.lastname: Chin
authors.forename: Janet
authors.initials: J
authors.lastname: Sim
authors.forename: Keng Ing
authors.initials: KI
authors.lastname: Seah
authors.forename: Tiow Suan
authors.initials: TS
authors.lastname: Sim
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008958:Models, Molecular; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism; D013302:Streptomyces / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D019751:Intramolecular Transferases; C038371:deacetoxycephalosporin C synthetase