Gregoriou M, Brown P R
Eur J Biochem. 1979 May 2;96(1):101-8. doi: 10.1111/j.1432-1033.1979.tb13018.x.
The time-dependent inhibition of amidase from Pseudomonas aeruginosa strain AI 3 by urea, hydroxyurea and cyanate displayed saturation kinetics fitting a model for the reaction sequence in which formation of a complex in a reversible step was followed by an irreversible step. Altered amidases from mutant strains AIU 1N and OUCH 4, selected for their resistance to inhibition of growth by urea and hydroxyurea respectively, had altered kinetic constants for inhibition indicating reduced binding capacity for the inhibitors. The substrate acetamide protected AI 3 amidase against inhibition by urea,.and altered Ki values for inhibition of the mutant amidases were paralleled by alterations in Km values for acetamide indicating that urea acted at the active site. Inhibition of AI 3 amidase involved the binding of one molecule of urea per molecule of enzyme. Urea inhibited amidase slowly regained activity at pH 7.2 through release of urea.
尿素、羟基脲和氰酸盐对铜绿假单胞菌AI 3菌株酰胺酶的时间依赖性抑制呈现出饱和动力学，符合一个反应序列模型，即在一个可逆步骤中形成复合物，随后是一个不可逆步骤。分别从对尿素和羟基脲生长抑制具有抗性的突变菌株AIU 1N和OUCH 4中获得的改变的酰胺酶，其抑制动力学常数发生了变化，表明对抑制剂的结合能力降低。底物乙酰胺可保护AI 3酰胺酶免受尿素抑制，突变酰胺酶抑制的改变的Ki值与乙酰胺的Km值变化平行，表明尿素作用于活性位点。AI 3酰胺酶的抑制涉及每分子酶结合一分子尿素。在pH 7.2时，尿素抑制的酰胺酶通过尿素的释放缓慢恢复活性。
