Pepsins and Pepsinogens

Pepsins and Pepsinogens.—The carbohydrate compositions and some sequences of amino-acids have been determined for glycopeptides derived from pepsinogens isolated from Japanese monkeys. Glycopeptides released by successive treatments of pepsinogen I with thermolysin and aminopeptidase contained 2-amino- 

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RIBULOSE-5-PHOSPHATE 3-EPIMERASE PEPSINS and PEPSINOGENS Peptide bond(s),... 

T2. Tang, J., and Tang, K., The heterogeneous nature of hog pepsin and pepsinogen. Federation Proc. 19, 330 (1960). Abstr. 

V3a. Van Vunakis, H., and Herriott, H. M., Structural changes associated with the conversion of pepsinogen to pepsin. II. The N-terminal amino acid residues of pepsin and pepsinogen the amino acid composition of pepsinogen. Biochim. Biophys. Acta 23, 600-608 (1957). 

If the molecular weights of pepsin and pepsinogen are 35,000 and 38,000, respectively (61), each of these molecules contains one atom of phosphorus (28, 60). Since it had been shown that ovalbumin and a-casein are readily dephosphorylated by certain phosphatases from mammalian tissue, and from potato, the action of these enzymes on pepsin and its precursor w as studied. It was found that only the potato phosphatase at pH 5.6 de-phosphorylates pepsin and pepsinogen, whereas prostate phosphatase does not act on these proteins. The intestinal enzyme, although not active at pH 6.0, liberates phosphorus at pH 8.9 (67). 

Action of Potato Phosphatase on Pepsin and Pepsinogen Each reaction mixture contained 1% protein and 0.003% enzyme in sodium acetate buffer of pH 5.6 and 0.1 r/2. 

The failure of the prostate enzyme to dephosphorylate pepsin and pepsinogen made it appear likely that the phosphate group in these proteins is not a monoester of the 0—type. Pretreatment of pepsin with a diesterase permits subsequent dephosphorylation with the prostatic enzyme, and it thus becomes clear that the phosphorus of this protein is present as a diester of the —O—P— 0— type. 

The work carried out in our laboratory on the macromolecular conformation of pepsin and pepsinogen and its relation to the biological function would hardly have been possible without the active contribution of some of my collaborators. I acknowledge the help of S. Beychok in the dichroism experiments and my sincere thanks go to William F. Harrington and Aharon Katchalsky for many helpful discussions which made a vital contribution to this investigation. Most of all, I like to remember the friendship of the late K. Linderstrpm-Lang. 

Figure 2-2. Roger Herriott s 1962 diagrammatic sketch of the pepsin and pepsinogen amino acid structure. (Reproduced from Herriott RM, Pepsinogen and pepsin. / Gen Physiol 45 57-76, 1962, by copyright permission of the Rockefeller University Press.)...

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