1] Swine pepsin and pepsinogen

Abstract

Publisher Summary This chapter discusses the determination of swine pepsin and pepsinogen. Swine pepsin is determined by the method, described by Anson, involves digestion of denatured hemoglobin by dilute pepsin under standard conditions after which the undigested protein is precipitated with TCA and this is then removed by filtration. The extent of digestion which is the measure of protease action is determined on the filtrate with the aid of Folin's phenol reagent. A blue color is produced by a reaction with the tyrosine and tryptophan of the protein split products in the filtrate. Conversion of the color value to units of pepsin is readily made from a standard curve. Swine pepsinogen may be determined in the presence of pepsin by destroying the latter at pH 8 where the precursor is stabile and then converting the pepsinogen into pepsin by acidification to pH 2. This pepsin is then assayed as described below. An evaluation of both components in a mixture of pepsin and pepsinogen entails two enzyme determinations, one after direct acidification which yields the sum of pepsin from pepsinogen and the initial pepsin, the other after first making the solution alkaline to pH 8 followed by acidification to pH 2 which measures the pepsinogen equivalent. The difference in the two values is the pepsin of the original mixture.