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A conformational model for the human liver microsomal glucose-6-phosphatase system: evidence from rapid kinetics and defects in glycogen storage disease type 1

Abstract : Rapid kinetics of glucose-6-phosphate (G6P) uptake and hydrolysis as well as of orthophosphate uptake were investigated in microsomes prepared from normal and glycogen storage disease type 1a (GSD 1a) human livers using a fast sampling, rapid filtration apparatus and were compared to those of rat liver microsomes. As shown before with rat microsomes, the production of [U-14C]glucose from 0.2 mmol/L [U-14C]G6P by untreated normal human microsomes was characterized by a burst in activity during the first seconds of incubation, followed by a slower linear rate. The initial velocity of the burst was equal to the rate of glucose production in detergent-treated microsomes. In untreated and detergent-treated GSD 1a microsomes, no glucose-6-phosphatase activity was observed. When untreated normal human or rat microsomes were incubated in the presence of 0.2 mmol/L [U-14C]G6P, an accumulation of [U-14C]glucose was observed, whereas no radioactive compound (G6P and/or glucose) was taken up by GSD 1a microsomes. Orthophosphate uptake was, however, detectable in both GSD 1a and normal untreated vesicles. These results do not support a rate-limiting transport of G6P in untreated normal human microsomes and further show that in this case of GSD 1a, no distinct G6P transport activity is present.
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https://hal.inrae.fr/hal-03324523
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Submitted on : Monday, August 23, 2021 - 4:36:55 PM
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J St-Denis, Blandine Comte, D Nguyen, E Seidman, K Paradis, et al.. A conformational model for the human liver microsomal glucose-6-phosphatase system: evidence from rapid kinetics and defects in glycogen storage disease type 1. Journal of Clinical Endocrinology and Metabolism, Endocrine Society, 1994, 79 (4), pp.955-959. ⟨10.1210/jcem.79.4.7962304⟩. ⟨hal-03324523⟩

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