Concanavalin A induced activity change in yeast PM-bound NADH-HCF(III) oxidoreductase

The activity of plasma membrane bound redox enzyme, NADH-HCF(III) oxidoreductase, in wild and mutant strains of the yeast Saccharomyces cerevisiae is modulated by Con A in a dose-dependent manner. The solubilized activity is enhanced at lower concentration and inhibited at higher concentration of Con A. The enzyme in mutant strain is more sensitive to inhibition. The activation of enzyme by Con A is suppressed in the presence of either alpha-methyl-D-mannoside or 2-deoxy-D-glucose, indicating the glycoproteic nature of enzyme as well as the resulting conformational change due to interaction with Con A as the factor for modulated activities. This was supported by recording the decrease in K(m) value of enzyme with respect to substrate NADH in the presence of lower concentration of Con A. The purified enzyme was more sensitive to lectin stimulation and, on the basis of comparative stimulatory effects of Con A and PSA on activity, it is likely that mannosyl moiety in enzyme is involved in binding the lectins to cause enzymic activation.