The effect of the modification of arginine side chains in casein on the coagulation of rennin-altered casein

Summary The modification of arginine residues in casein by treatment with glyoxal at pH 8·6 resulted in an inhibition of the coagulation of rennin-treated casein. The effective residues are on the κ-casein fraction and inhibition of coagulation was complete when about 1·5 residues of arginine/mole of κ-casein had been altered. It is suggested that the arginine forms part of a positively charged region that also includes lysine and histidine residues, and that this region is important in the coagulation of the casein.