Hydrolytic and Phosphorolytic Enzyme Activity and Reserve Mobilisation in Sprouting Tubers of Potato ( Solanum tuberosum L.)

Abstract

Summary The mobilisation of reserves and changes in associated enzyme activities have been examined in sprouting potato tubers. Although considerable depletion of both starch and protein was observed there were no substantial increases in the activities of β-amylase, starch phosphorylase, invertase, protease, or aminopeptidase. Although α-amylase activity was barely detected with the assay procedures used, an increase in activity accompanied starch breakdown. The rates of starch depletion were almost identical in tissues internal and external to the vascular ring but protein degradation was intially more rapid in the latter region. Starch phosphorylase activity was higher in the external tissues and β-amylase activity higher in the internal tissues. There were no consistent differences in the activites of invertase, protease, and aminopeptidase between these zones. While the maximum catalytic activity of starch phosphorylase was just sufficient to support the observed rates of starch depletion, activities of both α- and β-amylase were in appreciable excess.