Spontaneous and enzymatically catalyzed anomerization of glucose-6-P and anomeric specificity of related enzymes

Abstract

Enzymes acting on the first carbon of n-glucose are specific for a particular anomer. Two well known cases are the glucose oxidase from Penicillium not&urn and glucose dehydrogenase from liver, both of them specific for @-glucose1 (I, 2). It is likely that enzymes acting at the same level o f n-glucose 6-phos- phate will also have an anomeric specificity, but there was no definite information on this point, with the excepticn o f phos- phoglucomutases, which act on either a-n-glucose l-phosphate (3) or its /3 anomer (4). The rate o f spontaneous anomerization (mutarotation) of glucose and many other free sugars is rather slow at physiological pH (5) and there is an enzyme, mutarotase, that catalyzes the interconversion oc-n-glucose = P-n-glucose (6-8). However, there was no information on the rate of spontaneous anomerization of glucose B-phosphate or on the possibility of its enzymatic catalysis.