STUDIES ON CARBOHYDRATE METABOLIZING ENZYMES PART XXII. THE β-GLUCANASE SYSTEM OF MALTED BARLEY

Abstract

Extracts of malted barley have been shown by molecular sieve chromatography to contain at least five enzymes which hydrolyse β-glucosidic linkages. In order of decreasing molecular weight, these are two β-glucosidases, an endo-β-1,4-glucanase, an endo-barley-β-glucanase and an endo-β-1,3-glucanase. This last-named enzyme was purified about 60-fold and shown to be specific for substrates containing only β-1,3-glucosidic linkages. This enzyme was activated by calcium ions, and deactivated by EDTA, but was not affected by chloride ions or a sulphydryl reagent. The endo-β-1,4-glucanase, which was purified about 50-fold, hydrolysed glucans containing only β-1,4- or a mixture of β-1,3- and β-1,4-linkages. The two β-glucosidases were shown to be true glycosidases and not exo-β-glucanases. The changes which occur in the levels of the various enzymic activities during the malting process have been measured.