Carbohydrases of a rumen strain of Lactobacillus bifidus. 2. The intracellular α-1→6-glucosidase (isomaltodextrinase)

Abstract

Cell extracts prepared from a rumen strain of Lactobacillus bifidus, grown on dextran, contain an [alpha]-1[forward arrow]6-glucosidase that readily hydrolyses isomaltodextrins of degree of polymerization 2-9 to glucose. Hydrolysis of the isomaltodextrins is by the cleavage of single glucose units from the non-reducing end of the molecule. Isomaltodextrins of degree of polymerization 2-5 are hydrolysed at the same rate; as the degree of polymerization of the isomaltodextrins progressively increases above 5 the rate of hydrolysis decreases. The enzyme possesses optimum activity within the pH range 5.5-6.5, and temperature range 36-41[degree]; it may also act as a transferase if sufficient isomaltodextrin is present. The extracts also hydrolyze nigerose and a variety of [beta]-linked sugars but scarcely attack melibiose, maltose, turanose, leucrose, [alpha][alpha]-trehalose or methyl [alpha]-glucoside.