Tautomeric and anomeric specificity of allosteric activation of yeast pyruvate kinase by D-fructose 1, 6-bisphosphate and its relevance in D-glucose catabolism.

In aqueous solution Dfructose 1,6-bisphosphate (FBP)? exists as equilibrium mixture of 20 + 4% a-D-fructofuranose 1,6-bisphosphate, 80 f 10% /3-Dfructofuranose 1,6-bisphosphate, and less than 1.5% of the open chain [l-4] . The two anomeric forms are spontaneously interconvertible via the open chain tautomer. The first order rate constant for the ring opening of the o!-D-fructofuranose 1,6-bisphosphate is 0.55 set-’ at pH 7.6 and 25°C [4]. The terms ‘tautomeric’ and ‘anomeric’ are used here according to the definitions given in a previous report [5]. D-fructose 1,6-bisphosphate takes part in four reactions of D-glucose metabolism: it is the product of D-fructose-6-phosphate kinase, the substrate of