Stopped-flow kinetic studies of liver aldolase and of mixed liver-muscle aldolase catalyzed reactions of fructose 1, 6-bisphosphate (FBP) have been carried out and interpreted by computer simulation. These experiments indicate no utilization or binding of the α anomer by the liver enzyme unlike the findings for either the muscle aldolase which binds the a anomer nonproductively or the yeast aldolase which catalyzes its cleavage. Both β-fructose 1, 6-bisphosphate and its acyclic Most enzymes using sugar phosphates have now been examined for their specificity toward the anomeric or acyclic keto form may serve as substrates, necessitating the spontaneous anomerization of the α anomer before its utilization. Thus, liver aldolase cleaves 100% of the substrate present in the millisecond time scale because of the inability to bind α-FBP, allowing rapid spontaneous anomerization. This result fulfills earlier predictions of the differing specificities and substrate binding properties for aldolases from yeast, muscle, and liver.
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