The Binding of Enzymes to Fungal -Glucans

Abstract

Purified preparations of the extracellular glucan of Sphacelia sorghi and the walls of Claviceps purpurea contain enzymically active protein. The glucans and walls were treated in various ways to liberate the protein and determine the nature and strength of its binding, if any, to each matrix. Binding of protein to the glucan appeared to be non-covalent and was specific only in that the native protein seemed to bind more firmly than protein derived from other fungal genera. Binding of protein to walls appeared to be stronger than to the glucan but in each case protein was less stable when freed from its carbohydrate matrix. Protein liberated from glucan showed enhanced activity although its Km remained the same; thus, this matrix acted in the same manner as a non-competitive inhibitor. Protein liberated from walls was less active than when attached. The differences between the 2 matrices, with respect to protein binding, are discussed in the light of possible differences in their tertiary structure.