Two groups of intracellular α-amylase isoenzymes from cultured rice cells

Abstract

Abstract Two groups of α-amylase isoenzymes were purified and characterized from suspension cultured rice ( Oryza sativa cv Sasanishiki) cells. By native polyacrylamide gel electrophoresis, three activity bands were detected (amylase-I, -II and -III). Amylase-I and -II were charge isomers belonging to the same group with the same property. Amylase-III was electrophoretically homogeneous with a M r , of 40 000 and pI of 5.8. Cycloheptaamylose (β-CD)-Sepharose 6B has a specific affinity for amylase-III while amylase-I or -II were not absorbed on this column. Action patterns on soluble starch indicated that these amylases were all α-amylases. Significant differences between amylase-I (-II) and -III were found in K m values for soluble starch (1.1 mg ml −1 for amylase -I and 5.0 mg ml −1 for amylase-III), in M r , (42 000 for amylase-I and 40 000 for amylase-III) and in pI values (6.0 for amylase-I and 5.8 for amylase-III).