Peptide hydrolysis, catalyzed

S. A. Bizzozero, H. Dutler, Stereochemical Aspects of Peptide Hydrolysis Catalyzed by Serine Proteases of the Chymotrypsin Type , Bioorg. Chem. 1981, 10, 46 - 62 ... 

Fig. 31. Mechanistic proposal for peptide hydrolysis catalyzed by carboxypeptidase A (Christianson and Lipscomb, 1989). (a) The precatalytic Michaelis complex with substrate carbonyl hydrogen bonded to Arg-127 allows for nucleophilic attack by a water molecule promoted by zinc and assisted by Glu-270 (an outer-sphere C==O Zn interaction is not precluded), (b) Tbe stabilized tetrahedral intermediate collapses, with required proton donation by Glu-270 (Monzingo and Matthews, 1984) Glu-270 may play a bifunctional catalytic role (Schepartz and Breslow, 1987), which results in the product complex (c). [Reprinted with permission from Christianson, D. W., Lipscomb, W. N. (1989) Acc. Chem. Res. 22,62-69. Copyright 1989 American Chemical Society.]...

The COOH-terminal amino acid of a peptide or protein may be analyzed by either chemical or enzymatic methods. The chemical methods are similar to the procedures for NH2-terminal analysis. COOH-terminal amino acids are identified by hydrazinolysis or are reduced to amino alcohols by lithium borohydride. The modified amino acids are released by acid hydrolysis and identified by chromatography. Both of these chemical methods are difficult, and clear-cut results are not readily obtained. The method of choice is peptide hydrolysis catalyzed by carboxypeptidases A and B. These two enzymes catalyze the hydrolysis of amide bonds at the COOH-terminal end of a peptide (Equation E2.3), since carboxypeptidase action requires the presence of a free a-carboxyl group in the substrate. 

The stereochemical aspects of peptide hydrolysis catalyzed by chymotrypsin and related serine proteases has been recently analyzed with respect to requirements for stereoelectronic control of bond cleavage and this analysis has led to a much more complete understanding of the reaction mechanism (9-14). 

Scheme 14 Mechanism proposed for peptide hydrolysis catalyzed by thermolysin.

Bizzozero SA, Duller H (1981) Stereochemical aspects of peptide hydrolysis catalyzed by serine proteases of the chymotrypsin type. Bioorgan Chem 10 46-62... 

Figure 6.37 Peptide deformylase-catalyzed hydrolysis of N-formyl amino acids.

Figure 36 Complexes catalyzing hydrolytic cleavage of peptides, hydrolysis and alcoholysis of nitriles, decomposition of urea to carbon dioxide and ammonia, and alcoholysis of urea to ammonia and various...

M. N. James, and A. R. Sielecki, Stereochemical analysis of peptide bond hydrolysis catalyzed by the aspartic proteinase penicillopepsin, Biochemistry 24 3701 (1985). 

Fe ) catalyze ester and peptide hydrolysis as well as phosphoryl transfer proc-It has been stated in the context of short, strong hydrogen bonds, that the... 

The hydrolysis of peptide bonds catalyzed by the serine proteases has been the reaction most extensively studied by low-temperature trapping experiments. The reasons for this preference are the ease of availability of substrates and purified enzymes, the stability of the proteins to extremes of pH, temperature, and organic solvent, and the existence of a well-characterized covalent acyl-enzyme intermediate. Both amides and esters are substrates for the serine proteases, and a number of chromo-phoric substrates have been synthesized to simplify assay by spectrophotometric techniques. 

Thrombin [EC 3.4.21.5], also known as fibrinogenase, catalyzes the hydrolysis of peptide bonds, exhibiting preferential cleavage for the Arg—Gly peptide bond. The enzyme, a member of the peptidase family SI, activates fibrinogen to fibrin and releases fibrinopeptide A and B. Thrombin, formed from prothrombin, is more selective in peptide hydrolysis than trypsin or plasmin. 

In addition to the above-mentioned reactions, metal complexes catalyze decarboxylation of keto acids, hydrolysis of esters of amino acids, hydrolysis of peptides, hydrolysis of Schiff bases, formation of porphyrins, oxidation of thiols, and so on. However, polymer-metal complexes have not yet been applied to these reactions. 

Bamann et al.119 also found that the hydrolysis of di- and tri-peptides is catalyzed by rare earth ions at pH 8.6. Cerium(IV) and Cem were particularly effective even at a temperature of 37 °C. The same reactions with La111 as a catalyst were much slower and only occurred at an appreciable rate at 70 °C. Many of these reactions merit further study. 

Around 40% of the LMW fraction is absorbed from the small intestine in the rat (14). A part of the fraction may thus be present in the epithelial cells at the time of intracellular peptide hydrolysis. The effect of the LMW fraction on the activity of two cytosol enzymes, present in a preparation from hog intestine, is shown in Table III. Glycylleucine dipeptidase, which has a broad specificity (15), was inhibited at 0.7 mg/ml of the fraction, while proline cTTpeptidase, which catalyzes the hydrolysis of X-PRO (16), was not. 

The early work on inhibition of HIV-P was much influenced by previous structural and mechanistic work on pepsin and its inhibitors. Both enzymes are thought to catalyze peptide hydrolysis through a tetrahedral transition state, shown below as (29).The previous work... 

Initial attempts to achieve an enzyme-catalyzed deprotection of the carboxy group of peptides centred around the use of the endopeptidases chymotrypsin, trypsin,and thermolysin.P l Thermolysin is a protease obtained from Bacillus thermoproteolyticus that hydrolyzes peptide bonds on the annino side of the hydrophobic amino acid residues (e.g., leucine, isoleucine, valine, phenylalanine). It cleaved the supporting tripeptide ester H-Leu-Gly-Gly-OEt from a protected undecapeptide (pH 7, rt). The octapeptide, thus obtained, is composed exclusively of hydrophilic annino acids. Due to the broad substrate specificity of thermolysin and the resulting possibility of unspecific peptide hydrolysis, this method is of limited application. 

Proteins are hydrolyzed very slowly with storage in water at neutral pH. However, addition of proteases can increase the rate of hydrolysis about 10 billion times over the spontaneous rate. The chymotrypsin mechanism depicted in Figure 2.53 is shared by trypsin and elastase. These three proteases are members of a family called the serine proteases (named after Ser 195), Carboxypeptidase Aand pepsin catalyze peptide hydrolysis by different mechanisms and are not part of this family. 

Figure 10, Phenyl acetate inhibition of carboxypeptidase A-catalyzed hydrolysis of peptide, Dns-(Gly)g-i.-Phe, 1 X and the ester, Dns-(Gly)3-L.-0Phe, 4 X iO M (57), Enzyme concentrations were 5 X iO" and 4 X IO" M for ester and peptide hydrolysis, respectively (48, 57). Assays were performed in the absence (dashed Une) and presence (solid line) of 1 X phenyl acetate, 0Ac, at 25°C and...

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