Commercially available purified yeast ADH, horse liver ADH (both from Sigma) and purified maize ADH (ADH-2F) from our laboratory were subjected to the ADH-specific inhibitor (Ho and Scandalios, 1975, Plant Physiol. 56:56) from different corn tissues. It was found that ADH from horse liver is almost totally insensitive to the inhibitor in all cases; however, yeast ADH exhibits a susceptibility similar to that of maize ADH (Table 1). In our previous report (IB 1976) we suggested that different isozymes may have different sensitivities to the endogenous inhibitor and that different variants of the same isozyme may have the same sensitivities. Although the specific mechanism(s) of the inhibitory effect observed in these studies remains ambiguous, our results indicate that the similarities of this enzyme, ADH (including isozymes), from different organisms may be examined on the basis of inhibitor sensitivity. Thus, the ADH-specific inhibitor presents a potential parameter for studying the possible structural divergence of enzyme molecules at the sub-unit level.
Yiu Kay Lai and John G. Scandalios
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