[Structure-function study of 1,4-alpha-glucan branching enzyme by limited trypsin treatment]

1.4-alpha-glucan branching enzyme (EC 2.4.1.18) from rabbit muscles with an essential 2.5S RNA component has been studied by limited trypsin treatment. Under a great variety of hydrolysis conditions the product resistant to subsequent action of trypsin was obtained. This product contains about 70% of protein and all 2.5S RNA of the original nucleoprotein and retains about 50% of original activity. Amino acids Composition showed, that the protein is of alkaline nature and is rich in lysine. The alkaline nature of protein remains unchanged after trypsinolysis. On the basis of these studies it was assumed that the presence of firmly attached to the protein 2.5S RNA protects the branching enzyme against more powerful trypsinolysis and hinders loss of activity of the branching enzyme.