Enzymic Degradation of Starch Granules in the Cotyledons of Germinating Peas

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Abstract
Starch, total α- and β-amylase, and phosphorylase levels and the zymogram patterns of these 3 starch-degrading enzymes were determined in the cotyledons of smooth pea (Pisum sativum L.) during the first 15 days of germination. Starch is degraded slowly in the first 6 days; during this time, α-amylase is very low, β-amylase is present at a constant level while phosphorylase gradually increases and reaches a peak on the fifth day. Beginning on the sixth day there is a more rapid degradation of starch which coincides with α-amylase production. One phosphorylase band and 2 β-amylase bands are present in the zymogram of the imbibed cotyledon. An additional phosphorylase band and 1 α-amylase band appear during germination. Seeds imbibed in benzyladenine, chloramphenicol, and in cycloheximide show retarded growth and slower starch degradation and enzyme production than the controls. We conclude that α-amylase is the major enzyme involved in the initial degradation of starch into more soluble forms while phosphorylase and β-amylase assist in the further conversion to free sugars.