THE ISOLATION OF α-AMYLASE FROM BARLEY AND MALTED BARLEY, AND A STUDY OF THE PROPERTIES AND ACTION-PATTERNS OF THE ENZYMES

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Abstract
α-Amylase has been isolated from barley and malted barley of the same sample of cereal. The barley α-amylase was purified free from other carbohydrases and phosphatase by a simple procedure involving heat-treatment to deactivate the β-amylase followed by fractionation with acetone at −5°C.; the specific activity of the enzyme was increased some 120-fold. Malted barley α-amylase was isolated similarly, although a final purification step involving the glycogen/amylase complex was used. The specific activity of this enzyme was increased some 140-fold. For both enzymes, the optimum pH was 5·5 and the optimum temperature 45–50°C. The malt α-amylase was inherently the more unstable, although stability could be maintained by the addition of inert protein or excess calcium ions. Inhibition of both enzymes was complete in the presence of mercuric chloride (10−3 — 10−4 m), and the conjoint action of trypsin and ethylenediaminetetraacetate. The rates of degradation of amylose by the two α-amylases have been followed viscometrically as a function of time. The results indicate that an initial random hydrolysis of the substrate occurs. Light-scattering measurements have enabled the initial rates of attack of the enzymes on amylose, amylopectin, and glycogen to be determined. The same trends in the production of oligosaccharides at the achroic point in the α-amylolysis of amylose were shown, and the specific action of the malted barley α-amylase on some oligosaccharides (G4, G7 — G10) has been studied. It is concluded that barley and malted barley α-amylase have identical properties and show the same action-patterns.