Metabolite-modulated complex formation between alpha-glycerophosphate dehydrogenase and lactate dehydrogenase.
A modified Hummel-Dreyer equilibrium chromatography technique was used to test the hypothesis that NADH induces the molecular association of lactate dehydrogenase (LDH) and alpha-glycerol-3-phosphate dehydrogenase (alpha-GDH). In the presence of a very limited NADH concentration, a unique elution profile with a new peak running immediately ahead of a trough at the free alpha-GDH elution position is obtained. The appearance of this peak-trough profile is physical evidence that reversible association between LDH and alpha-GDH occurs over a very limited range of free NADH concentrations. The association constant for this complex formation between LDH and alpha-GDH is estimated to be 2.0 microM-1. With the NADH concentration increased to saturation level, no evidence of binding is observed. Such concentration-dependent behavior suggests that the strong competition between LDH and alpha-GDH for the limited amount of NADH tends to promote the enzyme-enzyme contact in order to make the most efficient use of the shared metabolite. The experimental results described in this article make a convincing argument for a metabolite-modulated enzyme-enzyme interaction along this metabolic pathway.
Yong
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H
Department of Chemistry, University of Oregon, Eugene 97403.
Thomas
G A
GA
Peticolas
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WL
D001667:Binding, Competitive; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D009243:NAD / Q000378:metabolism / Q000494:pharmacology; D013053:Spectrophotometry
D009243:NAD; D005993:Glycerolphosphate Dehydrogenase; D007770:L-Lactate Dehydrogenase