Trypsin

I.U.B.: 3.4.21.4

Trypsin is a pancreatic serine protease with substrate specificity based upon positively charged lysine and arginine side chains (Brown and Wold 1973). It has been isolated from a number of sources including dogfish (Titani et al. 1975), moose (Stevenson and Voordouw 1975), whale (Bricteux-Gregoire et al. 1975), elephant seal (Bricteux-Gegoire et al. 1974), Streptomyces griseus (Jurasek and Smillie 1974; Olafson and Smillie 1975), canine (Ohlsson and Tegner 1973), African lungfish (Reeck and Neurath 1972), swine (Hermodson et al. 1973); Walker and Keil 1973), rat (Vandermeers et al. 1973), human (Mallory and Travis 1973; Figarell et al. 1975) The enzyme also exhibits esterase and amidase activities. Trypsinogen and trypsin have been reviewed by Walsh (1970).

Characteristics of Trypsin from Bovine Pancreas:

Molecular weight: Trypsinogen: 24,000 (Walsh and Neurath 1964). Trypsin: 23,800 (Cunningham 1954).

Composition: Trypsinogen has been shown to have certain intrinsic activity. See Knights and Light (1974) for further references. It is usually considered, however, as the inactive precursor of trypsin which may be activated by removal of a terminal hexapeptide to yield single-chain β-trypsin. Subsequent limited autolysis produces other active forms having two or more peptide chains bound by disulfide bonds. The predominant forms are α-trypsin, having two peptide chains and β-, a single chain. Different activity and thermal stability are shown by α- and β-trypsin.

Benzamidine prevents conversion of β to α (Beardslee and Zahnley 1973; Schroeder and Shaw 1968). Trypsin can, by chromatography, be separated into the α and β forms. (Jameson and Elmore 1974). See also Keil-Dlouhá et al. (1971) and Smith and Shaw (1969). It has been pointed out by Schroeder (1972) that the several active species of trypsin have different catalytic constants and molecular properties and are present in all regularly purified preparations.

The structure of trypsin and a molecular model have been reported by Stroud, Kay, and Dickerson (1971). Active site studies have been reported by Berliner and Wong (1974 and 1973), Wong and Shaw (1974), Liem and Scheraga (1974), Nishino et al. (1974), Chambers et al. (1974), >Royer and Uy (1973), et al. (1973), Robinson et al. (1973, Kasai and Ishii (1973), Brown and Wold (1973), and Keil-Dlouhá (1972).

Optimum pH: Approximately 8.0.

Extinction coefficient: = 14.3.

Isoelectric point: Trypsinogen: pH 9.3 (Walsh and Neurath 1964). Trypsin: pH 10.5 (Cunningham 1954).

Inhibitors: Trypsin is inhibited by organophosphorus compounds such as diisopropyl fluorophosphate and natural "trypsin inhibitor" from pancreas. Soybean, lima bean, and egg white are sources of inhibitors (see section on Trypsin Inhibitors). Chambers et al. (1974) found silver ion to be a potent inhibitor. Inhibition by benzamidine is reversible (Mares-Guia and Shaw 1965). Other reports on inhibitors include Gaudin and Stevens (1974), Krebs and Jacquot-Armand (1973), Moroi and Yamasaki (1974), Morgan et al. (1974) and Geratz et al. (1975).

Activators: The rate of trypsinogen conversion is enhanced by using lanthanide in place of calcium ions (Gomez et al. 1974).

Specificity: The protease activity of trypsin is highly specific toward positively charged side chains with lysine and arginine. See also Keil-Dlouhá et al. (1971a).

Stabilizers: Calcium ion retards trypsin autolysis and promotes activation of trypsinogen. Sipos and Merkel (1970) have reported on the calcium-trypsin complex. See also Griffiths and Brechner (1973).

Stability: Trypsin is stable as a dry powder at 5°C for years.