Effects of the germination time on enzyme stabilities in extracts from wheat endosperms

Seeds of wheat (Triticum aestivum L.) were germinated and endosperm samples were harvested at daily intervals. Various enzymes were investigated with respect to their stability "in vitro" and their susceptibility to proteolytic inactivation by endopeptidase activity, which increases during germination. The stability of some enzymes in endosperm extracts was not obviously influenced by germination time (e.g. acid Phosphatase, phytase, peroxidase, malate dehydrogenase). A decreasing stability during germination was observed for leucine aminopeptidase, pyrophosphatase and glucose-6-phosphate dehydrogenase. It appears likely that the accelerated inactivation of these enzymes in endosperm extracts from germinated wheat seeds was caused by the increased endopeptidase activity. Especially glucose-6-phosphate dehydrogenase can be considered as an interesting model enzyme to study proteolytic inactivation and its regulation.