Some regulation profiles of ornithine transcarbamylase synthesis in vitro.

The regulation profiles of OTCase (argF, argI) synthesis in vitro were investigated by using the in vitro system described in the accompanying paper. Addition of 2.6 mM arginine, crude repressor and partially purified repressor to the in vitro system demonstrated that lambdadargF-DNA-directed OTCase-FFF synthesis is more sensitive to the repressor than lambdapargI-DNA-directed OTCase-III synthesis. The effects of some low-molecular substances on FFF and III syntheses were investigated; guanosine 3'-diphosphate 5'-diphosphate (ppGpp) stimulated both syntheses while cAMP and guanosine 5'-tetraphosphate (Gpppp) were not effective on III synthesis and were slightly inhibitory for FFF synthesis. The substances had no effect on the maturation of the enzyme or on the activity of the enzyme, FFF or III, synthesized. We suggest that argF- and argI-genes are regulated in a slightly different fashion and that the operator-promotor regions are not completely identical for these two genes.