Catalytic Reactions of Phosphoglucose Isomerase with Cyclic Forms of Glucose 6-Phosphate and Fructose 6-Phosphate

• Published in: The Journal of biological chemistry Vol. 248; no. 6; pp. 2219 - 2224
• Main Authors: Schray, K J, Benkovic, S J, Benkovic, P A, Rose, I A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 25-03-1973
• Subjects: Binding Sites; Chemical Phenomena; Chemistry; Ethers, Cyclic; Fructosephosphates; Furans; Glucose-6-Phosphate Isomerase - antagonists & inhibitors; Glucosephosphate Dehydrogenase; Glucosephosphates; Kinetics; Mathematics; Models, Chemical; Pyrans; Saccharomyces cerevisiae - enzymology; Stereoisomerism; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)44208-7

Yeast phosphoglucose isomerase is shown to use and produce both the α and the β anomeric forms of fructofuranose 6-phosphate.
Rapid quench techniques show a 20-fold preference in the utilization of the α anomer over the β anomeric form. The previous
report that the α anomer of glucopyranose-6-P is the preferred substrate form is confirmed. However the β anomer is also shown
to react at a slower rate. Studies using active site labeled phosphoglucose isomerase suggest that both anomers of each substrate
react at the same enzyme site. A reaction mechanism consistent with these observations involves opening of both α and β ring
forms to the corresponding acyclic forms followed by isomerization via an identical enzyme-bound cis -enediol. In order to accommodate both the α and the β anomers, torsion around C—C bonds is envisioned for the β anomers to
arrive at the same cis -enediol intermediates.