The degradation of zein during germination of corn was investigated in special relevance to protease activity. Polyacrylamide gel electrophoresis demonstrated that two main subunits of zein were rapidly degraded as the germination proceeded. It was observed that the zein degradation was followed by the formation of free amino acids, especially phenylalanine and tyrosine. A protease activity increased remarkably during the germination. A crude extract was obtained which could degrade zein in vitro to form relatively large amounts of free phenylalanine and tyrosine. The crude extract showed a maximum activity for casein at pH 3 and for zein at pH 4.5. The activity was enhanced when determined in the presence of 2-mercapto-ethanol. A sulfhydryl protease was estimated to occur which might be responsible for the degradation of zein during germination.

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