Design of mechanism-based carboxypeptidase A inactivators on the basis of the X-ray crystal structure and catalytic reaction pathway [1]
作者:Kyung Joo Lee、Dong H. Kim
DOI:10.1016/s0968-0896(98)00082-0
日期:1998.9
The X-ray crystal structure of the complex of carboxypeptidase A (CPA) and Gly-Tyr, has been documented. The crystal structure reveals that both the amide carbonyl oxygen and the terminal amino nitrogen of Gly-Tyr coordinate to the active site zinc ion of CPA in a bidentate fashion, whereby the zinc-bound water molecule is displaced by the amino group. As to the catalytic mechanism of CPA, it is generally
羧肽酶A(CPA)和Gly-Tyr的复合物的X射线晶体结构已被记录。晶体结构表明,酰胺羰基氧和Gly-Tyr的末端氨基氮均以二齿形式与CPA的活性位点锌离子配位,从而使结合锌的水分子被氨基置换。关于CPA的催化机理,一般认为,在酯底物的情况下,Glu-270的羧酸盐起亲核试剂的作用,可攻击易裂的羰基碳(酸酐途径),而在肽底物的情况下,锌-结合的水分子攻击易裂肽键(一般碱基途径)。根据X射线晶体结构和拟议的酶催化机理,可以预见,O-(羟基乙酰基)-L-β-苯基乳酸(L-1)的酯键将通过Glu-270的羧酸盐的攻击而水解以生成酸酐中间体。后者的中间体随后将受到羟基的攻击而引发的分子内重排,从而导致与Glu-270羧酸酯形成酯键。这种酯的形成会损害CPA的催化活性。我们已经使用动力学分析证明,L-1实际上是Kinact / KI值为0.057 M-1 s-1的酶的灭活剂。我们还证明了N-(羟乙酰