Abstract:

Some properties of rat liver amylase were studied. It was confirmed that this enzyme is located mainly in the microsomal fraction and that it is activated by detergents. The effects of digitonin, Triton X-100 and sodium deoxycholate on the amylase were compared. It was observed that amylase requires a higher concentration of Triton X-100 for maximal activation than lysosomal acid phosphatase. When lysosomes and microsomes were submitted to a detergent treatment capable of activating completely acid phosphatase and α-amylase, the former was solubilized, while the second remained particulate. The activation of α-amylase was found to be reversible in the first stages. The microsomal α-amylase is not bound to glycogen in fed rats. It was observed that the free α-amylase did not change when the liver was induced to accumulate different amounts of glycogen by administration of sugar, but that latent amylase was doubled when large amounts of glycogen accumulated. The Km of liver amylase for glycogen is 2.5 mg/ml as compared with 0.4 mg/ml for serum amylase. The significance of these observations is discussed. © 1968.