Inhibition of peptic digestion of serum albumin by fatty acids

At pH 5.4 “fatty-acid-free” BSA is digested about 50% more rapidly by pepsin than is BSA. Digestion of both is strongly inhibited either by transient exposure of the substrate to sodium caprylate-caprylic acid prior to mixing with pepsin or by addition of sodium caprylate-caprylic acid to the digestion mixture at a constant total electrolyte concentration. The latter inhibition occurs at all pertinent pH values. Apparently, binding of fatty acids by serum albumin causes a conformational rearrangement resulting in refractoriness to peptic hydrolysis. These results provide additional evidence for the specificity of the complex between pepsin and BSA observed previously by moving-boundary electrophoresis.