Chemical biology study on protein phosphatases and their specific inhibitors.

参与信号转导的蛋白质在增殖、分化和凋亡过程中都受到磷酸化/去磷酸化的调节。目前已经开发了许多蛋白激酶的选择性抑制剂，但还没有实现选择性磷酸酶抑制剂的开发。为了解决这个问题，我试图开发磷酸酶抑制剂。1.4-异香草酸内酯被分离出来作为VHR蛋白酪氨酸磷酸酶的抑制剂。由于4-异构胞内酯具有活性的外亚甲基部分，4-异构胞内酯可能通过直接修饰催化部位的半胱氨酸残基来抑制VHR。由于双专一性磷酸酶在催化部位具有共同的CXXXXXR基序，所以双专一性磷酸酶对4-异构胞苷很敏感。2.链霉菌产生的磷乳菌素(PLM)是丝氨酸苏氨酸磷酸酶的有效和选择性抑制剂，结合稳定同位素标记的环己烷羧酸(CHC)的掺入研究表明，链霉菌HK-803产生的6个PLM类似物(PLM A-F)都是由CHC起始单位生物合成的。PLM B的CHC衍生侧链的羟基化和随后的酯化反应产生了剩余的PLM类似物。对产生菌的整个75 kb的PLM生物合成基因簇进行了克隆、测序和分析，该簇包含6个基因(plML-7)，包括I型模块化PLM多酮合成酶的负载域和7个延伸模块。

Proteins involved in the signal transduction are regulated by phosphorylation/dephosphorylation during a process of proliferation, differentiation and apoptosis.Many selective inhibitors for protein kinases have been developed, however development of selective phosphatase inhibitors has not been achieved yet.To resolve this problem, I have tried to develop phosphatase inhibitors.1.4-isovavenaciolide was isolated as an inhibitor of the VHR protein tyrosine phosphatase. As 4-isoavenaciolide possesses a reactive exo-methylene moiety, it is possible that 4-isoavenaciolide inhibits VHR through the direct modification of a cysteine residue in the catalytic site.Since dual-specificity phosphatases have a consensus CXXXXXR motif in the catalytic site, dual-specificity phosphatases are sensitive to 4-isoavenaciolide.2.Phoslactomycins (PLMs) produced by Streptomyces, are potent and selective inhibitors of serine threonine phosphatases, PP2A.Incorporation studies with stable isotope labeling cyclohexanecarboxylic acid (CHC) indicated that the six PLM analoges (PLM A-F) made by Streptomyces sp.HK-803 are all biosynthesized from a CHC starter unit.Hydroxylation of the CHC-derived side chain of PLM B and a subsequent esterification produces the remaining PLM analogs.The entire 75 kb PLM biosynthetic gene cluster of the producing strain was cloned, sequenced and analyzed.Thecluster contains six genes (plml-7) which comprise the loading domain and seven extension modules of the type I modular PLM polyketide synthase.