Baĭkov A A, Smirnova I N, Volk S E
Biokhimiia. 1984 May;49(5):807-13.
Two forms of inorganic pyrophosphatase isolated from the inner membrane and matrix of beef heart mitochondria as well as from the inner membrane of rat liver mitochondria lose their activity during incubation with NaF in the presence of a magnesium salt and PPi. The inactivation occurs in two steps. First, the F- ion combines with an enzyme-substrate complex in a readily reversible process with a dissociation constant of approximately 3 mM. Then, the ternary complex undergoes slow isomerization with a rate constant of 5 min-1. The half-time of the inhibitor dissociation from the complex is 8 min. The enzyme SH-group modification with maleimides or a disulfide enhances the affinity to F- at the first step. The F- ion incompetitively inhibits PPi hydrolysis. The mechanism of fluoride toxicity and the use of fluoride in the studies of PPi metabolism are discussed.
从牛心线粒体的内膜和基质以及大鼠肝线粒体的内膜中分离出的两种形式的无机焦磷酸酶，在镁盐和焦磷酸存在的情况下与氟化钠一起孵育时会失去活性。失活过程分两步进行。首先，氟离子与酶 - 底物复合物结合，这是一个易于逆转的过程，解离常数约为3 mM。然后，三元复合物进行缓慢的异构化，速率常数为5 min⁻¹。抑制剂从复合物中解离的半衰期为8分钟。用马来酰亚胺或二硫化物对酶的巯基进行修饰会在第一步增强对氟离子的亲和力。氟离子非竞争性抑制焦磷酸水解。本文讨论了氟化物毒性的机制以及氟化物在焦磷酸代谢研究中的应用。
