title: Characterization of two ornithine carbamoyltransferases from Pseudomonas syringae pv. phaseolicola, the producer of phaseolotoxin.
abstract: Two ornithine carbamoyltransferases (OCT 1 and OCT 2) were isolated from Pseudomonas syringae pv. phaseolicola and purified by precipitation with ammonium sulfate, heat denaturation, chromatography on DEAE-Sephadex A-50 and Sephadex G-200. Molecular weights of both enzymes: 110,000; optimal activity: pH 8.5 to 9.5 (OCT 1), pH 8.4 (OCT 2); apparent Km for ornithine: 7 X 10(-4) (both enzymes); apparent Km for carbamoyl-phosphate: 7 X 10(-4) (OCT 1), 2.8 X 10(-3) (OCT 2). Both enzymes possess only an anabolic function. OCT 1 is highly inhibited by low concentrations of phaseolotoxin and Orn-P(O)(NH2)-NH-SO3H, OCT 2 is insensitive to both compounds. The inhibition of OCT 1 is reversible.
mesh_terms: D005098:Exotoxins / Q000096:biosynthesis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D009952:Ornithine / Q000031:analogs & derivatives; D009954:Ornithine Carbamoyltransferase / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D011549:Pseudomonas / Q000201:enzymology*
chemical_list: D005098:Exotoxins; C021234:phaseolotoxin; D009952:Ornithine; D009954:Ornithine Carbamoyltransferase