Exoamylase Activity in Vacuoles Isolated from Pea and Wheat Leaf Protoplasts

Abstract

ABSTRACI Vacuoles isolated from pea (Pisum sativum), and wheat (Triticum aestivum) leaf protoplasts contained considerable activities of electro-phoretically highly mobile exoamylases. Vacuoles from spinach (Spina-cia oleracea) leaf and photoautotrophic Chenopodium rubrum suspension culture cell protoplasts were devoid of amylolytic activity. Endoamylase activity was in all cases associated primarily with the chloroplast. Although amylases are considered to cooperate with phospho-rylases in the degradation of the transitory starch accumulated in chloroplasts (3), their overall physiological role in leaves is far from clear. Several reports suggest the presence of considerable activities of these enzymes outside the chloroplast (7, 10, 12, 15). No extrachloroplastic homoglucans which could act as substrates for such amylases are known and no explanations have been tendered to account for the presence of these enzymes outside the chloroplast in which transitory starch turnover is known to take place. The precise intracellular location ofextrachloroplastic amylases is not known (15), and a more definite assessment of their compartmentation is required in order to understand their significance for the assimilatory cell. We have analyzed subcel-lular fractions obtained from the protoplasts of both leaf and photoautotrophically growing suspension culture cells to acquire more insight into the compartmentation of amylases in