The separation of limit dextrinase from R-enzyme and aspects of the activities of the separated enzymes

Abstract

1. 1. Fractionation of malt enzymes by selective elution from an alumina column yields two enzymes which appear to be capable of attacking branched linkages in amylopectin or its degradation products. Two similar enzymes are present in R-enzyme concentrates from broad beans. 2. 2. The first enzyme, limit dextrinase, hydrolyzes the 1,6-α-glucosidic bonds in α-limit dextrins, which contain 5–8 glucose residues and are produced by the action of salivary α-amylase on amylopectin, and appears to be without action on larger substrates. It does not degrade isomaltose, isomaltotriose, and other substrates containing almost exclusively 1,6-linkages, and appears to require a substrate containing both 1,4-α- and 1,6-α-bonds. 3. 3. The second enzyme attacks amylopectin and β-limit dextrin, making increased β-amylolysis possible and effecting an increase in the blue values of the substrates. On the other hand, it fails to attack the above mentioned α-limit dextrins. The malt R-enzyme resembled generally the R-enzymes of broad beans and potatoes but appeared to be more specific in its attack on the outer branches of the substrates, producing very small amounts only of maltose and maltotriose even after prolonged attack. 4. 4. The limit dextrinase and malt R-enzyme each had a temperature optimum of 40 ° and had pH optima of 5.1 and 5.3, respectively. Molybdate ions completely inhibited the action of R-enzyme but not that of limit dextrinase. 5. 5. It is proposed to retain the name R-enzyme exclusively for the second enzyme.