Deamidation of Soy Peptides and Proteins by Bacillus circulans Peptidoglutaminase

The ability of Bacillus circulans peptidoglutaminase to deamidate soy proteins was investigated. Peptidoglutaminase readily hydrolyzed the γ‐amide of glutamine residues in soy peptides, but its activity toward soy proteins was low (0.4–1.3% deamidation). Molecular size and conformation of soy protein may be critical to enzymatic deamidation. Gel adsorption was used to partially purify the enzyme. Gel eluates exhibited higher acitivty than the cell extract toward soy peptides and all soy proteins but US globulin. The specific activity of the gel eluate toward 7S globulin and a water extract of soy flakes was doubled over the original cell extract.