Bandyopadhyay U, Kaiser T, Rudolf M T, Schultz C, Guse A H, Mayr G W
University of Hamburg, Dept. of Enzyme Chemistry, Germany.
Biochem Biophys Res Commun. 1997 Nov 7;240(1):146-9. doi: 10.1006/bbrc.1997.7629.
Inositol 1,2,3,5,6-pentakisphosphate (Ins(1,2,3,5,6)P5) 5-phosphatase present in fetal calf thymus has been partially purified. This enzyme was inhibited dose-dependently by different thiol modifiers like N-ethylmaleimide (NEM), p-chloromercuribenzene sulfonate (PCMBS), diamide, and phenylarsine oxide (PAO). The inhibition by PCMBS and diamide was protected by preincubation with dithiothreitol (DTT) and the phosphatase substrate, Ins(1,2,3,5,6)P5. Diamide, a compound that specifically modifies vicinal thiol groups, also blocked the 5-phosphatase dose-dependently. Specificity of this blockade was proven by using dimercaptopropanol (DMP), a compound known to protect vicinal thiol groups. DMP prevented the enzyme from inhibition by diamide. These data suggest that vicinal thiols are involved in Ins(1,2,3,5,6)P5 5-phosphatase activity.
