The enzymatic synthesis of protein. III. The effect of the hydrogen ion concentration on peptic synthesis

In two previous communications the authors have described a synthesis of protein by pepsin in a concentrated peptic hydrolysate of albumin (1); and the effect of temperature on this synthesis (2). The justification for describing the synthetic product as protein is discussed in our previous paper (2). In these communications the optimum hydrogen ion concentration was stated to be pH 4.0; but the influence of the hydrogen ion concentration was otherwise not discussed. The importance of the degree of acidity was realized early by Sawjalow (3), who did not, however, define it precisely, and by Henriques and Gjaldbäk (4), who gave the optimum pH as 1.5. This hydrogen ion concentration in our experience, despite the existence of all other optimum conditions, allows only very small amounts of synthesis. Either Henriques and Gjaldbäk were in error, or the occurrence of the optimum pH at 1.5 was due to some as yet unrecognized factor