Glucose 6-phosphate and mannose 6-phosphate are equally and more actively hydrolyzed by glucose 6-phosphatase during hysteretic transition within intact microsomal membrane than after detergent treatment

Archives of Biochemistry and Biophysics
A Ajzannay, G Mithieux

Abstract

We have studied the rapid kinetics of glucose-6-phosphatase (Glc6Pase) toward glucose 6-phosphate (Glc6P) and mannose 6-phosphate (Man6P) in intact and detergent-treated microsomes, using a radiometric assay based on the use of [U(-)14C]hexose 6-phosphates. We show that a hysteretic transition of Glc6Pase from a rapid hydrolytic form to slower kinetic form within the intact membrane occurs for both substrates with the same relaxation time. During the hysteretic transition, preceding the steady-state rate of hydrolysis, Glc6Pase is able to hydrolyze both Glc6P and Man6P at very similar rates. Only Glc6P is significantly hydrolyzed at steady state. Moreover, the initial rates of hydrolysis of both Glc6P and Man6P in intact microsomes are higher than the respective rates of hydrolysis after detergent treatment of the membrane at high substrate concentrations (10 and 20 microM), while these rates are not different at lower substrate concentrations. These data show that the marked specificity of Glc6Pase at steady state in the membrane is acquired owing to a hysteretic transition induced by the hydrolytic phenomenon, independently of the nature of the prior phosphate donor. The role of the membrane in this phenomenon is crucial, sin...Continue Reading

Citations

Mar 7, 2002·The Biochemical Journal·Emile van Schaftingen, Isabelle Gerin
Mar 11, 2000·European Journal of Biochemistry·G van de WerveA Berteloot
Aug 3, 2004·Microscopy Research and Technique·Othon B KotoulasDimitrios J Kondomerkos
Nov 13, 2004·American Journal of Physiology. Endocrinology and Metabolism·T TaguchiI Miwa
May 23, 1997·The Journal of Biological Chemistry·G BánhegyiA Benedetti
Jul 30, 1997·Biochemical and Biophysical Research Communications·B Annabi, G van de Werve

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