title: New type of hexameric ornithine carbamoyltransferase with arginase activity in the cephamycin producers Streptomyces clavuligerus and Nocardia lactamdurans.
abstract: The ornithine carbamoyltransferases (OTCases) from the beta-lactam-producing actinomycetes Streptomyces clavuligerus and Nocardia lactamdurans have been purified to near-homogeneity by delta-N-phosphonoacetylornithine-Sepharose 4B affinity chromatography. The S. clavuligerus and N. lactamdurans OTCases monomers had a molecular mass of 37 kDa. The native OTCases of S. clavuligerus, N. lactamdurans and Streptomyces coelicolor had molecular masses of 248, 251 and 247 kDa respectively, which correspond to a hexameric structure. The apparent K(m) values for ornithine and carbamoylphosphate of the S. clavuligerus enzyme were respectively 2.3 and 6.0 mM at pH 8.0. The enzyme showed a reverse activity on citrulline and used lysine and putrescine as substrates. The hexameric complex showed coupled arginase-OTCase activities and was able to convert arginine into citrulline in a carbamoylphosphate-dependent manner. The requirement for carbamoylphosphate might prevent the arginase-OTCase complex from carrying out a futile cycle of arginine biosynthesis and degradation.
authors.affiliation: Department of Ecology, Genetics and Microbiology, Faculty of Biology, University of León, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: De la Fuente
authors.forename: J F
authors.initials: JF
authors.lastname: Martin
authors.forename: P
authors.initials: P
authors.lastname: Liras
mesh_terms: D000494:Allosteric Regulation; D001119:Arginase / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D001704:Biopolymers; D002513:Cephamycins / Q000096:biosynthesis*; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D007700:Kinetics; D008970:Molecular Weight; D009615:Nocardia / Q000201:enzymology* / Q000378:metabolism; D009954:Ornithine Carbamoyltransferase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001704:Biopolymers; D002513:Cephamycins; D001120:Arginine; D009954:Ornithine Carbamoyltransferase; D001119:Arginase