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Abstract

A modified cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase is produced by the method of single point substitution in a native cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme, whereby the substitution: a) maintains enzyme specificity by conserving the active site groove of the native cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme; and b) effects increased thermostability over the native cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme by: i) replacing glycine by proline or alanine in helices of the cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme, in order to stiffen the enzyme amino acid chain and reduce entropy of the unfolded enzyme; ii) attaching negatively charged residues to N-termini of helices in the native cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme; iii) introducing ion pairs into the native cereal (1.fwdarw.3,1.fwdarw.4)--.beta.-glucanase enzyme, to increase binding energy in the folded enzyme; iv) replacing lysine by arginine in the cereal (1.fwdarw.3,1.fwdarw.4)-.be-ta.-glucanase enzyme, and thereby preventing lysine glycation and increasing hydrogen bonding with other parts of the enzyme; v) replacing, by glycine, an amino acid in the native cereal (1.fwdarw.3,1.fwdarw.4)-.beta.-glucanase enzyme in which the main chain torsion angle about the N and C.sup..alpha. atoms is greater than 0.degree.; or vi) creating cysteine pairs in the native cereal (1.fwdarw.3,1.fwdarw.4)-.-beta.-glucanase enzyme which can form disulphide bonds across the C and N terminals.

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