The kinetics of Ins(1,4)P2 dephosphorylation by Ins(1,4)P2 1-phosphatase in bovine brain.
Ins(1,4)P2 1-phosphatase catalyses the dephosphorylation of Ins(1,4)P2 to Ins(4)P. This enzyme was purified 3000-fold to a specific activity of 10-20 mumol/min/mg protein. Ins(1,4,5)P3 (0.04-1 microM) was not a substrate of the enzyme under conditions where 50% of Ins(1,4)P2 was dephosphorylated. All kinetics of Ins(1,4)P2 1-phosphatase displayed Michaelis-Menten behaviour. Both reaction products, Ins(4)P and phosphate inhibited the enzyme: Ins(4)P was a non-competitive inhibitor (Ki = 59 microM) and phosphate was competitive (Ki = 0.53 mM) with respect to Ins(1,4)P2 as substrate. In contrast, Li+ inhibition was uncompetitive (Ki at 1 mM LiCl was 2.7 mM).
Delvaux
A
A
Institut de Recherche Interdisciplinaire (I.R.I.B.H.N.), Université Libre de Bruxelles, Belgium.
Dumont
J E
JE
Erneux
C
C
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
D007295:Inositol Phosphates; C044259:inositol 1,4-bis(phosphate); D008094:Lithium; D010744:Phosphoric Monoester Hydrolases; C053087:inositol-1,4-bisphosphate 1-phosphatase