Kcat KM Values:catalytic efficiency催化效率 TABLE 8.7 I Enzymes for which kcat/Km is close to the diffusion-controlled rate of encounter Enzyme kcat/KM (s-1M-1) Acetylcholinesterase 1.6×108 Carbonic anhydrase 8.3×107 Catalase 4×107 Crotonase 2.8×108 Fumarase 1.6×108 Triose phosphate isomerase 2.4×108 B-Lactamase 1×108 Superoxide dismutase 7×109 Source:After A.Fersht,Structure and Mechanism in Protein Science:A Guide to Enzyme Catalysis and Protein Folding (W.H. Freeman and Company,1999),Table 4.5. 上述酶Kca/Ky ratios已达完美极限，催化速度仅受溶液扩 散速度的限制。kcat / KM Values: catalytic efficiency 催化效率 上述酶kcat/KM ratios已达完美极限，催化速度仅受溶液扩 散速度的限制