Muscle FBPase in a complex with muscle aldolase is insensitive to AMP inhibition

Abstract

Real‐time interaction analysis, using the BIAcore biosensor, of rabbit muscle FBPase–aldolase complex revealed apparent binding constant [K _Aapp] values of about 4.4×10⁸ M⁻¹. The stability of the complex was down‐regulated by the glycolytic intermediates dihydroxyacetone phosphate and fructose 6‐phosphate, and by the regulator of glycolysis and glyconeogenesis – fructose 2,6‐bisphosphate. FBPase in a complex with aldolase was entirely insensitive to inhibition by physiological concentrations of AMP (I _0.5 was 1.35 mM) and the cooperativity of the inhibition was not observed. The existence of an FBPase–aldolase complex that is insensitive to AMP inhibition explains the possibility of glycogen synthesis from carbohydrate precursors in vertebrates’ myocytes.