The inhibition of plant phosphorylases by β-amylase and the detection of phosphorylase in barley

Abstract

Aqueous extracts of ungerminated barley convert glucose-1-phosphate into an ester resistant to hydrolysis by N acid in 7 min. with the simultaneous release of some inorganic phosphate. No iodine-staining polysaccharides are produced. Extracts of wheat, oats, rye and barley grains inhibit the activity of broad-bean and potato phosphorylase. The inhibitory power is related to the amt. of beta-amylase present, and is destroyed by heating the extracts. Soya-bean beta-amylase and crystalline beta-amylase from the sweet potato (Balls) have the same inhibitory effect. The inhibition is not due to destruction of primer by beta-amylase. Phosphorylase can be detected in extracts of ungerminated barley made at pH 6.8, after fractionation and concn. with ammonium sulfate. This procedure reduces the ratio of beta-amylase to phosphorylase to a level where inhibition is only partial.