Yamaguchi A, Nemoto M, Adachi A, Inaba T, Sawai T
J Antibiot (Tokyo). 1986 Dec;39(12):1744-53. doi: 10.7164/antibiotics.39.1744.
When Citrobacter freundii cephalosporinase was incubated with 6 beta-[3-(2-chlorophenyl)-5-methyl-4-isoxazolyl]penicillin sulfone (cloxacillin sulfone) in phosphate buffer, the enzyme was suddenly inactivated just after the completion of enzymatic degradation of the cloxacillin sulfone. Such delayed inactivation was due to a secondary inhibitor formed from cloxacillin sulfone during the incubation period. The inactivation was delayed due to the protection of the enzyme by cloxacillin sulfone from the attack of the secondary inhibitor. Phosphate anions were essential for the formation of the secondary inhibitor. However, once the secondary inhibitor was formed, the inactivation occurred in the absence of phosphate anions although the degree of the inactivation depended on the length of the preincubation period with phosphate anions. The main species (more than 80%) of the inactivated enzyme was detected as a single protein band with a slightly lower pI value than that of the native enzyme on isoelectric focusing on a plate.
将弗氏柠檬酸杆菌头孢菌素酶与6β-[3-(2-氯苯基)-5-甲基-4-异恶唑基]青霉素砜（氯唑西林砜）在磷酸盐缓冲液中孵育时，在氯唑西林砜的酶促降解刚完成后，该酶就突然失活。这种延迟失活是由于在孵育期间由氯唑西林砜形成了一种二级抑制剂。由于氯唑西林砜对酶的保护作用，使其免受二级抑制剂的攻击，失活被延迟。磷酸根阴离子对于二级抑制剂的形成至关重要。然而，一旦二级抑制剂形成，即使失活程度取决于与磷酸根阴离子预孵育的时间长短，在没有磷酸根阴离子的情况下也会发生失活。在平板等电聚焦上，失活酶的主要种类（超过80%）被检测为一条单一的蛋白带，其pI值略低于天然酶。
