Studies on gastric proteolysis. 1. The proteolytic activity of human gastric juice and pig and calf gastric mucosal extracts below pH 5

Wh, Taylor

doi:10.1042/bj0710073

Cited by 52 publications

(6 citation statements)

References 8 publications

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“…By contrast, the gastric juice of the same patients and extracts of their uninvaded gastric mucosa digested plasma proteins with two pH maxima, at pH 2-1-2.4 and pH 3.3-3-8, thus showing the same proteolytic properties as normal gastric juice and normal gastric mucosal extracts under the same experimental conditions (Taylor, 1959a).…”

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confidence: 85%

The Proteinases of Human Gastric Adenocarcinomata: Their Identification, Separation and Sites of Action on the B-Chain of Oxidized Insulin

Etherington

Taylor

1972

Clinical Science

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S U M M A R Y1. Because of the possibility that the proteinases of gastric adenocarcinomata may differ from those of healthy gastric mucosa, an investigation of these enzymes by means of pH-activity studies, agar-gel electrophoresis, column chromatography and the mode of action on the B-chain of oxidized insulin has been undertaken.2. Agar-gel electrophoresis of extracts at pH 5 revealed a single zone of proteinase activity situated at the equivalent position to the zone 7 of normal gastric mucosal extracts and not activated at pH 2. The typical pepsins of normal mucosal extracts were not present.3. Agar-gel electrophoresis at pH 8.2 resolved this single zone into three zones. One was located slightly cathodally (proteinase 1) and the other two anodally (a slower proteinase 2A and a faster 2B).4. Proteinases 2A and 2B were separated by column chromatography and shown to have identical asymmetrical broad pH-activity curves with the maximum at pH 3.3-3.4. 5. Proteinase 1 had a symmetrical narrow pH-activity curve with the maximum at pH 3.7-3-9. Proteinase 1 was purified and resolved into two highly active major components, 1A and lB, by column chromatography, first on DEAE-cellulose and then on CM-cellulose.6. The sites of cleavage of the B-chain of oxidized insulin were determined for proteinases 1A and 1B. The same bonds were split by each, with one exception, but several were split at differing rates indicating that the two enzymes had related, but different, modes of action.7. The tumour proteinases 1 resemble the cathepsins D in certain respects and the pepsins in others. They may represent an enzyme structure of an intermediate form.There is insufficient evidence to indicate whether they are elaborated by partially differentiated cells or whether they are derived from cells which have become dedifferentiated. No enzymes exactly like them have yet been found in normal tissues.

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The Proteinases of Human Gastric Adenocarcinomata: Their Identification, Separation and Sites of Action on the B-Chain of Oxidized Insulin

Etherington

Taylor

1972

Clinical Science

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“…The pepsin was that of gastric juice obtained from a patient suffering from a gastric ulcer. The pH of the reaction mixture was adjusted using varying proportions of buffers, 01 M glycine HCl or 0-2 M acetate HCI buffers, as described by Taylor (1959a).…”

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pH stability and activity curves of pepsin with special reference to their clinical importance.

Piper¹,

Fenton²

1965

Gut

339

200

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EDITORIAL SYNOPSIS A study of the effect ofpH on the stability and activity of pepsin showed that 70 % of maximal peptic activity was still present at pH 4 5 and that pepsin was irreversibly inactivated at pH 8. The clinical implications of these findings are discussed.The concept of peptic ulceration and its treatment is based on the ulcerogenic action of acid and pepsin (Card, 1952). It appears that pepsin plays the predominant role in this action (Schiffrin, 1940; Schiffrin and Warren, 1942; Le Veen, 1947), the acid merely providing the correct pH for optimal peptic activity. Consequently, it is of some importance to know the effect of pH on the peptic activity of pepsin. One of these effects, the effect of pH on peptic activity, has been adequately studied (Christensen, 1955; Taylor, 1959a, b and c); the effect of pH on enzyme stability has received little attention apart from the observations of Langley in the last century (Langley, 1881a and b) and those of Northrop, Kunitz, and Herriott (1948). As both of these effects are of considerable importance in clinical gastroenterology, the present study was undertaken of the effect of pH on the stability and activity of pepsin. METHODSEFFECT OF pH ON THE STABILITY OF PEPSIN Solutions of pepsin were incubated at 37°C. for 10 minutes at varying pH levels, then titrated to pH 2 and peptic activity estimated using the radioiodinated serum albumin method (Klotz and Duvall, 1957;Piper, 1960). The peptic activity in these reaction mixtures was compared, after corrections had been made for the dilution involved in the back titration, with the peptic activity of a standard solution that had not been incubated at any different pH. The solutions of pepsin used were Parke Davis reference pepsin (400 mg. %) and unpurified solutions of human pepsin obtained from the homogenate of human gastric fundic mucosa.As the time the pepsin was at the high pH could be crucial, a solution of Parke Davis reference pepsin and of human pepsin was incubated at pH 7-2 for varying times (1, 2-5, 5, 10, 20, 40, and 60 min.) and the effect on peptic activity on restoration to pH 2 determined as above.EFFECT OF pH ON PEPTIC ACTIVITY A pH activity curve for human pepsin was determined using radioiodinated serum albumin as substrate and the method previously described (Piper, 1960). The pepsin was that of gastric juice obtained from a patient suffering from a gastric ulcer. The pH of the reaction mixture was adjusted using varying proportions of buffers, 01 M glycine HCl or 0-2 M acetate HCI buffers, as described by Taylor (1959a). RESULTSThe result of the studies on the effect of pH on peptic activity and stability is shown in Figure 1. The pH stability curve in this figure represents that of pepsin in human fundic mucosa; Parke Davis reference pepsin gave an identical curve. These results show that pepsin is stable at pH ranges as high as pH 6. Above this pH, pepsin is rapidly irreversibly inactivated and elevation of pH of the reaction mixture to pH 8 results in complete inactivation of pepsin...

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“…Salivary amylase coupled with acid hydrolysis initiates the splitting of starch and dextrin to dissacharides, and pepsin-HCl and pepsins occurring in abnormal conditions (Taylor, 1959) convert dietary protein to proteoses and peptones (Wright, 1952). The importance of gastric juice in preparing starch and protein for further digestion in a readily assimilable form was appreciated by early gastric physiologists (Lancet, 1960) and has not been questioned.…”

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Hydrolysis of fat by human gastric juice

Bank¹,

Krut²,

Marks³

et al. 1964

Gut

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Studies on gastric proteolysis. 1. The proteolytic activity of human gastric juice and pig and calf gastric mucosal extracts below pH 5

Cited by 52 publications

References 8 publications

The Proteinases of Human Gastric Adenocarcinomata: Their Identification, Separation and Sites of Action on the B-Chain of Oxidized Insulin

The Proteinases of Human Gastric Adenocarcinomata: Their Identification, Separation and Sites of Action on the B-Chain of Oxidized Insulin

pH stability and activity curves of pepsin with special reference to their clinical importance.

Hydrolysis of fat by human gastric juice

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