Caselli A, Camici G, Manao G, Moneti G, Pazzagli L, Cappugi G, Ramponi G
Dipartimento di Scienze Biochimiche, Università di Firenze, Italy.
J Biol Chem. 1994 Oct 7;269(40):24878-82.
The low M(r) phosphotyrosine protein phosphatase (PTPase) and Yersinia enterocolitica PTPase are inactivated by nitric oxide-generating compounds. Inorganic phosphate, a competitive inhibitor, protects the enzymes from inactivation, suggesting that the action of NO is directed to the active sites. Low M(r) PTPase from bovine liver lost two out of eight thiol groups present in the molecule during the inactivation with sodium nitroprusside and with other NO-producing compounds. The mass spectrometric analyses of tryptic fragments of the enzyme, performed after chemical modification of the NO-unreacted thiol groups, demonstrated that NO caused the oxidation of Cys-12 and Cys-17 to form an S-S bond. A similar reaction was described previously for the reaction of NO with N-methyl-D-aspartate receptor. The NO-inactivated low M(r) PTPase was reactivated by treating the inactive enzyme with thiol-containing reagents. Since all members of the PTPase family have the same reaction mechanism and possess a conserved active site motif that contains an essential cysteine residue, the findings on low M(r) and Yersinia PTPases are potentially interesting for all PTPases, an enzyme class that is involved in a number of important biological processes.
低分子量磷酸酪氨酸蛋白磷酸酶（PTPase）和小肠结肠炎耶尔森菌PTPase可被产生一氧化氮的化合物灭活。无机磷酸盐作为一种竞争性抑制剂，可保护这些酶不被灭活，这表明一氧化氮的作用是针对活性位点的。在用硝普钠和其他产生一氧化氮的化合物使来自牛肝的低分子量PTPase失活的过程中，该分子中存在的八个巯基中的两个丧失。在用未与一氧化氮反应的巯基进行化学修饰后，对该酶的胰蛋白酶片段进行质谱分析，结果表明一氧化氮导致半胱氨酸-12和半胱氨酸-17氧化形成二硫键。先前曾描述过一氧化氮与N-甲基-D-天冬氨酸受体反应的类似反应。通过用含巯基的试剂处理无活性的低分子量PTPase，可使其重新激活。由于PTPase家族的所有成员都具有相同的反应机制，并且拥有一个包含必需半胱氨酸残基的保守活性位点基序，因此关于低分子量PTPase和耶尔森菌PTPase的研究结果可能对所有PTPase都具有潜在意义，PTPase是一类参与许多重要生物学过程的酶。
