Turnover of genetically defined catalase isozymes in maize.

The turnover of two homotetramers of catalase, V(4) and Z(4), specified by genes at two separate loci, has been studied during germination of maize seed by the techniques of density labeling and starch-gel electrophoresis. Both isozymes were shown to be turning over during this time. However, Z(4) accumulates because the rate of synthesis exceeds the rate of degradation, whereas V(4) slowly disappears because the rate of degradation exceeds the rate of synthesis. Evidence is also presented that the rate of synthesis of Z(4) exceeds that of V(4), which suggests that this may be a major factor in the differential expression of the two catalase genes.