REGULATION AND KINETICS OF 2 ORNITHINE TRANSCARBAMYLASE ENZYMES OF BACILLUS LICHENIFORMIS

1. 1. The regulation of the two ornithine transcarbamylase enzymes (carbamol-phosphate; l-ornithine carbamoyltransferase, EC 2.1.3.3) of Bacillus licheniformis was studied. Ornithine transcarbamylase I is repressed by l-arginine, l-citrulline and l-ornithine during growth on glucose. Ornithine transcarbamylase II is induced by l-arginine (but not by l-citrulline or l-ornithine) in post-logarithmic phase cells or in cells growing on glutamate. Glucose addition represses this induction in the glutamate medium. 2. 2. The ornithine transcarbamylase I was purified about 10 fold and ornithine transcarbamylase II about 8 fold. 3. 3. The two ornithine transcarbamylases have the same pH optimum (8-9) and no significant differences could be detected in Michaelis-Menten constants for either substrate. 4. 4. The back reaction (citrulline → ornithine) was not catalyzed by either ornithine transcarbamylase. 5. 5. Arginine deiminase was not detected in extracts of these cells. 6. 6. The physiological role of the inducible ornithine transcarbamylase (ornithine transcarbamylase II) is not known. © 1968.