Liver aldolase anomeric specificity.

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 alpha anomer by the liver enzyme unlike the findings for either the muscle aldolase which binds the alpha anomer nonproductively or the yeast aldolase which catalyzes its cleavage. Both beta-fructose 1,6-bisphosphate and its acyclic keto form may serve as substrates, necessitating the spontaneous anomerization of the alpha anomer before its utilization. Thus, liver aldolase cleaves 100% of the substrate present in the millisecond time scale because of the inability to bind alpha-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.