Bolivar F, Galván M, Martuscelli J
J Gen Microbiol. 1976 May;94(1):142-8. doi: 10.1099/00221287-94-1-142.
An unusual Escherichia coli K12 mutant for carbamyl phosphate synthetase is described. The mutation was generated by bacteriophage MUI insertion and left a 5% residual activity of the enzyme using either ammonia or glutamine as donors. The mutation is recessive to the wild-type allele and maps at or near the pyrA gene, but the mutant requires only arginine and not uracil for growth. By a second block in the pyrB gene it was possible to shift the accumulated carbamyl phosphate to arginine biosynthesis. The Km values and the levels of ornithine activation and inhibition by UMP were normal in the mutant enzyme.
描述了一种不寻常的用于氨甲酰磷酸合成酶的大肠杆菌K12突变体。该突变由噬菌体MUI插入产生，使用氨或谷氨酰胺作为供体时，该酶保留了5%的残余活性。该突变对野生型等位基因是隐性的，定位在pyrA基因处或其附近，但该突变体生长仅需要精氨酸而不需要尿嘧啶。通过pyrB基因中的第二个阻断，可以将积累的氨甲酰磷酸转移到精氨酸生物合成中。突变酶的米氏常数以及鸟氨酸的激活水平和UMP的抑制作用均正常。
