Seed germination studies I. Purification and properties of an [alpha]-amylase from the cotyledons of germinating peas

Abstract

A starch-hydrolyzing enzyme present in extracts of the cotyledons of germinating peas has been purified over 3400-fold. Several independent criteria show that this activity is due to an amylase of the [alpha]-type ([alpha]-1,4-glucan-4-glucanohydrolase, EC 3.2.1.1). The enzyme exhibits maximal activity in the pH range 5.3-5.9; the Michaelis constant (Km) and energy of activation (Ea) for the enzyme-catalyzed reaction are 2[middle dot]10-4 g soluble starch per ml and 7600 cal/mole, respectively. Calcium ions protect the amylase against heat inactivation, whereas incubation of the enzyme with 5[middle dot]10-4 M EDTA for 20 min at room temperature results in complete loss of activity. With amylose and amylopectin as substrates, this enzyme is similar in action pattern to other known plant [alpha]-amylases.