Substrate‐Induced Dissociation of Glycerol‐3‐phosphate Dehydrogenase and Its Complex Formation with Fructose‐bisphosphate Aldolase

Abstract

A threefold decrease in specific activity of glycerol‐3‐phosphate dehydrogenase was found on going from 800 nM to 10 nM enzyme concentration. According to ultracentrifugal analyses the dimeric glycerol‐3‐phosphate dehydrogenase (molecular weight 78000) dissociates into monomers in the equilibrium mixture of its substrates and products. The concentration‐dependent decrease in the specific activity is interpreted as a consequence of subunit dissociation and the estimated dissociation constants are 0.7 μM and 3.5 μM at 38°C and 20°C respectively. According to active‐enzyme‐band centrifugation experiments and kinetic analysis aldolase forms a complex with glycerol‐3‐phosphate dehydrogenase and this complex formation influences the specific activity of the dehydrogenase. The interaction between glycerol‐3‐phosphate dehydrogenase and aldolase can provide a regulatory mechanism at the branching point of glycolytic and lipid metabolic pathways. Copyright © 1980, Wiley Blackwell. All rights reserved