title: Ornithine decarboxylase in Phycomyces: in vitro and in vivo properties.
abstract: The properties of ornithine decarboxylase from Phycomyces blakesleeanus were examined. Enzyme from mycelial cultures was extracted and purified approximately 70-fold. The apparent molecular weight is 96K. The Michaelis constants with respect to ornithine and pyridoxal 5'-phosphate are 90 and 0.37 microM, respectively. Putrescine is a potent competitive inhibitor with a Ki of 75 microM. Exposure of ornithine decarboxylase to sulfhydryl-modifying reagents resulted in a rapid inhibition of activity. In vivo addition of putrescine produced characteristic decreases in cellular ornithine decarboxylase activity. Light stimulation of dark-adapted mycelial cultures also decreased cellular ornithine decarboxylase activity.
mesh_terms: D002262:Carboxy-Lyases / Q000302:isolation & purification*; D055598:Chemical Phenomena; D002621:Chemistry; D005033:Ethylmaleimide / Q000494:pharmacology; D005658:Fungi / Q000201:enzymology*; D007700:Kinetics; D009955:Ornithine Decarboxylase / Q000302:isolation & purification*; D065108:Ornithine Decarboxylase Inhibitors; D010775:Photic Stimulation; D010800:Phycomyces / Q000201:enzymology* / Q000254:growth & development; D011700:Putrescine / Q000494:pharmacology
chemical_list: D065108:Ornithine Decarboxylase Inhibitors; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase; D005033:Ethylmaleimide; D011700:Putrescine