Ullah A H, Sethumadhavan K
Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Boulevard, New Orleans, Louisiana, 70124, USA.
Biochem Biophys Res Commun. 1998 Oct 9;251(1):260-3. doi: 10.1006/bbrc.1998.9456.
Myo-inositol hexasulfate (MIHS), a structural analog of the substrate myo-inositol hexaphosphate, is a potent competitive inhibitor of both phyA and phyB enzymes. The Ki of inhibition for the phyA and phyB proteins were estimated to be 4.6 and 0.2 microM, respectively. Thus, the phyB protein is 23-fold more sensitive to MIHS inhibition than the phyA protein. The active-site geometry of phyB protein is presumed to be very different from the phyA protein as deduced by chemical probing of the enzymes by Arg-specific modifiers, i.e., 1,2-cyclohexanedione and phenylglyoxal. Probing the catalytic site of the same proteins by this newly developed specific inhibitor also gives a similar conclusion.
肌醇六硫酸盐（MIHS）是底物肌醇六磷酸的结构类似物，是phyA和phyB酶的强效竞争性抑制剂。对phyA和phyB蛋白的抑制常数（Ki）估计分别为4.6和0.2微摩尔。因此，phyB蛋白对MIHS抑制的敏感性比对phyA蛋白高23倍。通过精氨酸特异性修饰剂（即1,2 - 环己二酮和苯乙二醛）对酶进行化学探测推断，phyB蛋白的活性位点几何结构与phyA蛋白非常不同。用这种新开发的特异性抑制剂探测相同蛋白的催化位点也得出了类似的结论。
