生物化学：第四章 酶(8周1节) (1).pdf

回顾上次课程内容 四．酶的结构和催化作用机制 3. 催化作用机制 （2 ）酶作用高选择性的机制 （3 ）酶作用高效率的机制 活化能降低 邻近效应与定向效应 6种催化机制 4. 实例 溶菌酶 丝氨酸蛋白酶 本次课主要内容 四、酶的结构和催化作用机制 4. 实例 碳酸酐酶 五、酶的调控 1. 别构调控 2. 共价修饰调控 3. 酶原的激活 六、人工酶与酶工程(自学为主) 四、酶的结构及催化作用机制 4. 实例 （3）碳酸酐酶carbonic anhydrases k1 = 0.15 s-1, k-1 = 50 s-1. K1 = 5.4 ×10-5 [CO ] : [H CO ] = 340 : 1 2 2 3 （3）碳酸酐酶(carbonic anhydrase) Carbonic anhydrase are required because CO hydration and H CO dehydration are 2 2 3 often coupled to rapid processes, particularly transport processes. Mutations in some carbonic anhydrases have been found to cause osteopetrosis (骨骼石化 症) (excessive formation of dense bones accompanied by anemia) and mental retardation (智力延迟). Carbonic Anhydrase Contains a Bound Zinc Ion Essential for Catalytic Activity The structure of human carbonic anhydrase II and its zinc site Catalysis Entails Zinc in Activation of Water A group with pKa = 7 plays an important role. The deprotonated (high pH) form of this group participates more effectively in catalysis. ? Mechanism of carbonic anhydrase A synthetic analog model system for