Research / Clinical Summary

Percy Russell, BS, MA, PhD Emeritus Professor, Biological Sciences Contact by Email

Our research projects involve the role of vitamin C In glucose metabolism in rabbit skeletal muscle. We have shown that μmolar concentrations of vitamin C are capable of specifically inhibiting three purified muscle enzymes (adenylate kinase mAK, lactate dehydrogenase (mLDH), and 1-phosphofructokinase (mPFK-1)). None of the other enzymes in the glycolytic pathway were inhibited by very high concentrations (10 mM) of vitamin C. The three muscle isozymes have been shown to have important roles in the control of glycogen synthesis and glycolysis. The vitamin C inhibitions appear to be muscle specific. We have not been able to demonstrate vitamin C inhibitions in blood, liver and other tissues in some initial studies.

Our working hypothesis is that vitamin C inhibitions of these muscle isozymes facilitate storage of glucose as muscle glycogen during periods of rest and are not inhibited during periods of activity. Normally vitamin C concentrations in muscle are high enough (300 μmolar) to inhibit these enzymes. We have recently shown that the presence of another enzyme in the glycolytic pathway, aldolase, protects these enzymes from vitamin C inhibition. Others have shown that muscle enzymes in the glycolytic pathway bind and release from myosin and actin depending on the active or rest state, respectively. The general consensus is that the bound enzymes are in their most active form. We are currently preparing studies to determine the effect of myosin, troponin, tropomoysin, F- and G-actin on vitamin C inhibitions of mAK, mLDH, and mPFK-1. We believe that these observations are related to control of glucose metabolism and to diabetes.

Keywords: Vitamin C inhibition, muscle isozymes, adenylate kinase, lactate dehydrogenase, 1-phosphofructokinase, vitamin C, glycogen synthesis, glycolysis, actin, myosin, muscle proteins, diabetes.