Pepsinogen plasma

Pepsinogen. This precursor of the proteolytic enzyme pepsin is secreted by gastric parietal cells pepsinogen activities may be increased following peptic ulceration and by parasitic infections. The enzyme may be measured in plasma or gastric fluid using colorimetric, fluorimetric, or radioimmunometric methods and ELISA methods (Will et al. 1984 Ford et al. 1985 Tani et al. 1987 Lynch et al. 2004). 

Days Gastric Pepsin (U 24 hr" ) Urine Hydroxycorticoids (mg 24 hr Urine Pepsinogen (Uhr- ) Plasma Pepsinogen (U%) Creatinine Clearance (L24 hr" ) Pepsinogen Clearance (L24 hr" )... 

Leonard Johnson, working with me as a graduate student after my return to Michigan, demonstrated that back-diffusion of acid liberates histamine within the mucosa. Liberated histamine stimulates acid secretion and increases mucosal capillary permeability, with the result that the mucosa sheds plasma proteins of all molecular weights. In addition, Johnson showed later that back-diffusion of acid stimulates secretion of pepsinogen through a cholinergic reflex. 

Hirschowitz BI, Streeten DHP, London J A, et al. Effects of eight-hour intravenous infusion of ACTH and adrenal cortical steroids in normal men. I. Basal gastric secretion, and plasma and urinary pepsinogen. J Clin Invest 36 1171-1182, 1957. 

An acid protease with an optimum pH of 2.5 was first described in human seminal plasma as pepsin and pepsinogen (1), but had not been purified or characterized. Recently, we have purified the acid protease and its proenzyme from human seminal plasma (2,3). In many respects, the properties of seminal plasma acid protease are similar to those of gastric pepsin. Since the proenzyme is more stable than the active enzyme in alkaline solution and can be converted into its active form in acidic solution, the acid protease is likely to exist in seminal plasma, at the physiological pH around 7.5 (4), in proenzyme form. 

Conversion of the proenzyme into its active form. We concluded that only the proenzyme form of acid protease can exist in human seminal plasma at the physiological pH of around 7.5 therefore, we investigated activation of proenzyme in acid medium. The purified proenzyme was incubated in 1 mM HCl, pH 3, for 1 hr, and then chromatographed on Sephadex G-50 column. The proenzyme was converted into an active form and some peptide of small molecular weight was released (Fig.2). As shown in Table II, when the amino acid analyses of the proenzyme, the active form, and activation peptide were carried out, the number of each amino acid residue of the proenzyme agreed well with the additive value between the number of that amino acid in the active form and activation peptide. This supported the conversion of the proenzyme to an active form. The amino acid composition of the active protease and of the proenzyme were comparable to those of bovine pepsin (10) and pepsinogen (11). However, definite differences are present. About forty residues which carried most of the basic amino acids, were released from pepsin, while sixty-nine residues, which carried about 30% of basic amino acid of the precursor were liberated from the proenzyme of seminal plasma acid protease. 

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