Bovine pancreas inhibitor

The structural analysis of the trypsin inhibitor from bovine pancreas (BPTI) in complex with trypsin shows that the inhibitor occupies and blocks the substrate binding pocket in a highly complementary maimer (fig. 2.9). In the trypsin-BPTI complex, the catalytically essential Ser-OH of trypsin contacts a CO group of the inhibitor in a manner very similar to the tetrahedral transition state of amide or ester bond hydrolysis (see fig. 2.9b). The inhibitor can be likened to a pseudo-substrate and, as such, is bound with high affinity. The cleavage of the peptide bond is, however, not possible due to other circumstances, such as the fact that water is prevented from reaching the active site with the inhibitor boimd. 

Soybean trypsin inhibitor 4.6 Trypsinogen (bovine pancreas) 9.3... 

This evidence has been reinforced recently by an elegant x-ray crystallographic study of the complex formed by trypsin and a polypeptide trypsin inhibitor of the bovine pancreas (25). The complex has proven to be a tetrahedral adduct which is stabilized by hydrogen bonds between the enzyme and the leaving group and by the inability of His-57 (see later) to assume a conformation which would enable it to protonate the leaving group. 

PS ll-membranes were prepared from pea leaves Pisum sativum) according to Berthold et al. [1 ] with the modification described in ref. [2]. The membranes were separated by a mild trypsin treatment. For this the membranes were diluted in low salt resuspension medium to a chlorophyll concentration of 100/ig/mi and incubated at room temperature with 2/ig/ml trypsin from bovine pancreas. After 5 min. trypsination was stopped by addition of a 20-fold excess of trypsin inhibitor and the preparation was concentrated by centrifugation. For the measurements the chlorophyll concentration of the sample was adjusted to 2 mg/ml yielding an optical density at 532 nm of 0.1. Photovottage measurements were carried out in a capacitive microcoaxial cell of 3x0.1 mm dimensions [3]. The excitation source was a frequency doubled Nd-YAQ laser delivering flashes at 532 nm of either 12 ns or 30 ps duration. Orientation by an... 

Three inhibitors from non-food sources are included in Table II. The basic (Kunitz) trypsin inhibitor from bovine pancreas (BPTI) is a small protein that has been used extensively in protein structure studies. At neutral or acid pH, it denatures near 100°C. From the ratio of calorimetric to van t Hoff (effective) enthalpies, Privalov... 

Inhibitor activity is normally determined with commercial animal enzymes, e. g., bovine trypsin or bovine chymotrypsin. The evaluation of a potential effect of the inhibitors on human health assumes that the inhibition of human enzymes is known. Present data show that inhibitors from legumes generally inhibit human trypsin to the same extent or a little less than bovine trypsin. On the other hand, human chymotrypsin is inhibited to a much greater extent by most legumes. Ovomucoid and ovoinhibitor from egg white as well as the Kazal inhibitor from bovine pancreas do not inhibit the human enzymes. The Kunitz inhibitor from bovine pancreas inhibits human trypsin but not chymotrypsin. The data obtained greatly depend not only on the substrate used, but also on the enzyme preparation and the reaction conditions, e. g., on the ratio enzyme/inhibitor. The stability of an inhibitor as it passes through the stomach must also be taken into account in the evaluation of a potential effect (cf. Table 16.15). The Kunitz inhibitor of soybeans, for... 

An inhibitor for trypsin bears the formidable name bovine pancreatic trypsin inhibitor (BPTl) (Voet and Voet, 1995, p. 396ff). It functions to keep trypsin from digesting the pancreas itself. The BPTI structure is said to resemble that of trypsin, the similarity causing a binding that cancels the enzymatic activity of trypsin. Again, we are talking of protease inhibitors. 

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