Proteolytic coefficient

Using four different peptides as substrates, Adams, et al.,21 found for 10 normal individuals the following ranges in activity (proteolytic coefficient x 104). 

Fig. 2. Effect of concentration of inhibitors on carboxypeptidase activity, following preincubation. Preincubation conditions Carboxypeptidase inhibitor, pH 7.5, 0°C., 60 minutes. Activity measurements 0.02 M CGP in veronal buffer containing 0.1 M NaCl, pH 7.5, 25°C. Activities were expressed as apparent proteolytic coefficients calculated from the strictly linear portions of first-order reaction plots.

The effects of increasing concentrations of 8-OHQ-5SA, OP, and aa D on the activity of carboxypeptidase at a constant substrate concentration of 0.02 M CGP are shown in Fig. 2. (Vallee and Neurath, 1955.) Activity of the inhibited reaction was expressed as per cent of the proteolytic coefficient observed at zero inhibitor concentration. The conditions of preincubation are indicated. Recent and unpublished data indicate the time course of the inhibitory effects of these agents OP in concentrations of 1 X 10" M causes 90 % inhibition of the reaction in 60 minutes. 80 % of the inhibition occurs in the first 15 minutes (Fig. 3), Addition of 1 X 10" M zinc ions to the enzyme thus inhibited restores enzymatic activity, demonstrating the reversibility of inhibition (unpublished results). Since inhibition did not occur when chelating agents were first incubated with zinc, cupric, or ferrous ions to form the respective metal chelate, it appeared that the sites of chelation of these compounds are responsible for the observed inhibition. Inhibition is therefore not caused by any structural similarity between the inhibitors and the substrate. 

The proteolytic coefficient is largest for compounds with N-terminal leucine and norleucine, but several other amino acids may be attacked at sufficient rates to make this enz3rme a generally useful reagent. Its activity is not restricted to small peptides, and it has been used in the stepwise degradation of proteins from the amino end, in the same manner that carboxypeptidase has been used in the analysis of the carboxyl ends of protein chains. 

Fig. 9. Effect of pH on the proteolytic coefficient (Ci) for the hydrolysis of benzoyl-L-argininanude by papain in the presence of 0.005 M cysteine (100). The buffers were present at 0.02 M except for citrate which was 0.04 M.

Fig. 10. Effect of pH on the activation of crystalline paptun as measured by the proteolytic coefficient (Ci) for the hydrolysis of bmiaoyl>L>argininamide (153). Activators were used singly and in various combinations. Cys is cys teine and V is Versene, all used at 0.005 Af. The buffers were used at 0.02 M concentration acetate near pH 5, citrate at pH 6, phosphate at pH 7, and Tris near pH 8. Cysteine plus Versene gave the highest activity at all pH ralues and the Cl values were independent of the buffer used.

The term proteasome is used to describe two kinds of multisubunit proteolytic complexes, the 26S and 20S, based on their sedimentation coefficient. The 26S proteasome degrades ubiquitinated protein substrates. The 26S complex contains the 20S as a core and regulatory caps on either end like a dumb bell. Each cap of the 26S proteasome is known as the 19S regulatory complex (19S RC). The 20S core is a cylindrical structure consisting of the catalytic part of the proteasome. ... 

Studies of other sources of ceruloplasmin may eventually prove useful in structure elucidation, but have already clarified some of the copper chemistry. Ceruloplasmin from goose serum has been isolated, purified, and characterized. This ceruloplasmin has less carbohydrate attached, but two forms may be isolated under some conditions. It is clear that these are not products of proteolytic degradation, but perhaps they might have a different carbohydrate attached. The two type I sites have higher extinction coefficients than type I sites in other ceruloplasmins, reflecting a modestly different environment (Hilewicz-Grabska et al, 1988). 

More detailed discussion of food polymers and their functionality in food is now difficult because of the lack of the information available on thermodynamic properties of biopolymer mixtures. So far, the phase behaviour of many important model systems remains unstudied. This particularly relates to systems containing (i) more than two biopolymers, (ii) mixtures containing denatured proteins, (iii) partially hydrolyzed proteins, (iv) soluble electrostatic protein-polysaccharide complexes and conjugates, (v) enzymes (proteolytic and amylolytic) and their partition coefficient between the phases of protein-polysaccharide mixtures, (vi) phase behaviour of hydrolytic enzyme-exopolysaccharide mixtures, exopolysaccharide-cell wall polysaccharide mixtures and exopolysaccharide-exudative polysaccharide mixtures, (vii) biopolymer solutes in the gel networks of one or several of them, (viii) enzymes in the gel of their substrates, (ix) virus-exopolysaccharide, virus-mucopolysaccharides and virus-exudative gum mixtures, and so on. 

Comparisons of the kinetic coefficients in Eq. (1) obtained from initial rate measurements with alternative substrates have given a considerable amount of information about reaction pathways as well as indications of the molecular basis of specificity (60). This approach, much used for proteolytic enzymes, has been exploited particularly with the alcohol dehydrogenases, which catalyze the oxidation of a variety of primary and secondary alcohols (61). While several other dehydrogenases have been studied in this way, most of the results have been reported only as apparent maximum rates and apparent Km values for the alternative substrate, which restricts the amount of information that can be derived. 

Mastitis is well known to decrease lactose content. This fact explains the relation between lactose content and determination of log SCC (4). This emphasizes the possibilities of detecting changes with lactose when analyzing milk spectra and proves its strong relation with SCC. Factors 5, 6, 8 and 10, which showed high correlation with regression coefficients, had the highest correlation with protein content. This is consistent with the fact that mastitis causes alteration of protein fractions in milk. Mastitic milk has more proteolytic activity than normal milk, due to increase of proteinase plasmin, which hydrolyzes the casein (25, 26). Harmon (6) and Urech et al. (25), have reported decreased ccs-casein and (3-casein content and elevated whey proteins and y-casein in the total protein of mastitic milk. 

The high temperature coefficient of the reversible heat inactivation indicates that the phemonenon is due to a reversible denaturation of a protein, as has been described for proteolytic enzymes by Kunitz and Northrop (140) and Anson and Mirsky (8). The large pressure effects are also indicative of a very large molecule. The quantitative relation between temperature and luminescence intensity at different pressures can be described satisfactorily (Fig. 7) on the simple theory that the intensity increases with rise in temperature in proportion to the rate of the reaction, in accordance with equation (1), while at the same time it decreases in proper-... 

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