Vicinal thiols are involved in inositol 1,2,3,5,6-pentakisphosphate 5-phosphatase activity from fetal calf thymus.
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.
Bandyopadhyay
U
U
University of Hamburg, Dept. of Enzyme Chemistry, Germany.
Kaiser
T
T
Rudolf
M T
MT
Schultz
C
C
Guse
A H
AH
Mayr
G W
GW
D000818:Animals; D001152:Arsenicals / Q000494:pharmacology; D001665:Binding Sites; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005333:Fetus; D007295:Inositol Phosphates / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013950:Thymus Gland / Q000201:enzymology*
D001152:Arsenicals; D004791:Enzyme Inhibitors; D007295:Inositol Phosphates; D013438:Sulfhydryl Compounds; C029341:oxophenylarsine; C013571:inositol pentaphosphate; C109214:inositol 1,2,3,5,6-pentakisphosphate 5-phosphatase; D010744:Phosphoric Monoester Hydrolases