Subtilisin and alpha-chymotrypsin catalyzed synthesis of peptides containing arginine and lysine p-nitroanilides as C-terminal moieties.

p-Nitroanilides of N-acylated di-, tri- and tetrapeptides with C-terminal arginine or lysine residues have been obtained, as a rule with good yields, via acylation of arginine or lysine p-nitroanilides by methyl esters of respective N-acylated peptides, catalyzed by subtilisin or alpha-chymotrypsin. The synthesis might be performed by two routes--by reaction in water-organic solvent mixtures, catalyzed by dissolved enzyme, or by condensation of the components in organic solvents with low water content in the presence of any enzyme distributed over a silica support surface. The second approach seems to be preferable due to suppression of hydrolytic side reactions and improved stability of an enzyme.

gamma-Glutamyltranspeptidase-catalysed acyl-transfer to the added acceptor does not proceed via the ping-pong mechanism.

Acyl-transfer catalysed by gamma-glutamyltranspeptidase from bovine kidney was studied using gamma-L- and gamma-D-Glu-p-nitroanilide as the donor and GlyGly as the acceptor. The transfer of the gamma-Glu group to GlyGly was shown to be accompanied by transfer of the gamma-Glu group to water (hydrolysis). The results were compared with acyl-transfer catalysed by the representative serine protease, alpha-chymotrypsin.

Side reactions in enzymatic peptide synthesis in organic media: effects of enzyme, solvent, and substrate concentrations.

The progress of enzymatic peptide synthesis catalyzed by alpha-chymotrypsin and subtilisin from Bacillus subtilis strain 72 (subtilisin 72) in low-water systems was studied. The initial reaction mixture consisted of the solvent, the acyl-group donor (MalAlaAlaPheOMe or ZAlaAlaPheOMe, Mal, maleyl, Z, benzyloxycarbonyl), the nucleophile XaaNH2 (Xaa = Phe, Leu or Ala), and the enzyme adsorbed on porous silica material. All amino acid residues were of the L-configuration.

Steady-state kinetics of glutamine cyclotransferase.

The reaction mechanism of papaya latex glutamine cyclotransferase was studied using pH and temperature dependencies, a proton inventory technique, and molecular modeling. The pH-dependence of the Michaelis-Menten parameters showed that the published pH dependence of the enzyme "activity" was mainly the result of pH-dependent change of the active (unprotonated) substrate concentration. The enzyme activity as such changed very slightly in the pH range between 4.

Nucleophile specificity in alpha-chymotrypsin- and subtilisin-(Bacillus subtilis strain 72) catalyzed reactions.

Nucleophilic properties of amino-acid amides were studied systematically in acyl-transfer reactions catalyzed by alpha-chymotrypsin and subtilisin from Bacillus subtilis strain 72 (subtilisin 72) using Mal-L-Ala-L-Ala-L-PheOMe as the acyl-group donor. In alpha-chymotrypsin-catalyzed reactions, the nucleophile reactivities increase in the following order: D-AlaNH2 < GlyNH2 < L-AlaNH2 < L-SerNH2 < L-ThrNH2 < L-HisNH2 < L-ValNH2 < L-LeuNH2 < L-TrpNH2 < L-MetNH2 < L-NvaNH2 < L-PheNH2 < L-IleNH2 < L-TyrNH2 < L-ArgNH2. In reactions catalyzed by subtilisin 72, the reactivities increase as follows: L-LeuNH2 < L-IleNH2 < L-ThrNH2 < L-ArgNH2 < L-TrpNH2 < L-NvaNH2 < L-ValNH2 < L-MetNH2 < L-AlaNH2 < L-SerNH2 < D-AlaNH2 < GlyNH2.

Organic solvent changes the chymotrypsin specificity with respect to nucleophiles.

In alpha-chymotrypsin-catalyzed acyl-transfer reactions in water the specificity of the enzyme (the nucleophile reactivity of amino acid amides) is correlated with the substrate hydrophobicity and increases as the hydrophobicity of the side chain of the amino acid amides is increased. In a low water system (4% H2O) bulky amino acid amides are less efficient nucleophiles. The specificity of alpha-chymotrypsin towards the amino acid amides in acyl transfer reactions in this case does not depend on the hydrophobicity of the amino acid side chains but correlates with their size.

Subtilisin from Bacillus subtilis strain 72. The influence of substrate structure, temperature and pH on catalytic properties.

Kinetic constants for the hydrolysis of the series of p-nitroanilide peptide substrates catalyzed by subtilisin from Bacillus subtilis strain 72 have been determined. The series of N-protected p-nitroanilides of the Z-A2-A1-pNA, Z-A3-A2-A1-pNA, Z-A4-A3-A2-A1-pNA types (Z-, benzyloxycarbonyl-1; -pNA, p-nitroanilide; A1-An, amino acid residues of the L-configuration) have been used. Subsite S1 reveals a preference for hydrophobic amino acid residues, i.

Increased nucleophile reactivity of amino acid beta-naphthylamides in alpha-chymotrypsin-catalyzed peptide synthesis.

Alpha-chymotrypsin-catalyzed acyl transfer from Boc-L-MetONp, Ac-L-TyrOEt, Bz-L-TyrOMe, Mal-L-PheOMe to the C-protected amino acids (L-AlaNH2, L-LeuNH2, L-ArgOMe and beta-naphthylamides of L-Arg, L-Leu, L-Ala and L-Glu) has been studied. Modification of the carboxylic groups with beta-naphthylamide was shown to increase the reactivity of nucleophiles in these reactions by a factor of more than 100 in comparison with amides and esters of the same amino acids. This effect can be accounted for by the effective formation of the nucleophile-acylenzyme complex due to hydrophobic interactions of the beta-naphthylamide moiety with the corresponding subsite of alpha-chymotrypsin.

Tyrosine phenol-lyase from Citrobacter intermedius. Factors controlling substrate specificity.

L-Amino acids are competitive inhibitors of tyrosine phenol-lyase from Citrobacter intermedius. For non-branched amino acids the correlation exists between -RTlnKi and side-chain hydrophobicity. Aspartic and glutamic acids are anomalously potent inhibitors taking into account low hydrophobicity of their side chains.

Plasteins. Their preparation, properties, and use in nutrition.

The theoretical and practical aspects of the plastein reaction, which consist in the formation of a gel following the addition of an endopeptidase to a concentrated solution of a partial protein hydrolysate, are examined and the properties and possibilities of using plasteins in nutrition are discussed. It is shown that valuable protein food products can be obtained with the aid of the plastein reaction from proteins with an unbalanced amino acid composition and from chemically synthesized amino acids. Other applications of plasteins in nutrition are discussed and the studies carried out hitherto on the mechanism and driving forces of plastein formation are considered.