Biomedical subjects

V M Stepanov

Publications and source records attributed to V M Stepanov.

At least 37 records · Page 2Linked to original sources

PubMed1997

Thiolsubtilisin as an instrument for peptide synthesis. Preparation and properties.

A convenient procedure for thiolsubtilisin purification from an admixture of subtilisin involving affinity chromatography on bacitracin-Sepharose is presented. Thiolsubtilisin activity was measured by hydrolysis of p-nitrophenyl acetate, p-nitroanilide-peptide (Glp-Ala-Ala-Leu-pNA), and azocasein. The thiolenzyme catalyzes peptide synthesis. Under these conditions only activated peptide esters, e.g., p-chlorophenyl, N-hydroxysuccinimide, or p-nitrophenyl esters form peptide bonds during interaction with appropriate nucleophiles such as peptides and their derivatives and amino acid amides.

Amino Acids↗

PubMed1997

Glutamyl endopeptidase of Bacillus intermedius strain 3-19. Purification, properties, and crystallization.

A homogeneous glutamyl endopeptidase splitting peptide bonds of glutamic and, rarely, of aspartic acid residues in peptides and proteins was isolated from Bacillus intermedius 3-19 culture filtrate using chromatography on CM-cellulose and Mono S. The enzyme molecular mass is 29 kD and the pI is 8.4. The proteinase is inhibited by DFP. The enzyme, like other glutamyl endopeptidases, reveals two pH optima (pH 7.5 and 9.0) for casein and one (pH 8.0) for Z-Glu-pNA hydrolysis. The K(m) for the hydrolysis of the latter substrate is 6 mM. The enzyme activity is optimal at 55 degrees C. The enzyme is stable in the pH range 6.5-11.0. Its N-terminal sequence shows 56% coinciding residues when compared with that of Bacillus licheniformis glutamyl endopeptidase. Crystal prisms or plates 0.25-0.3 x 0.15 x 0.07-0.1 mm have been grown using the vapor diffusion technique in a hanging drop followed by macroseeding. The crystals belong to the space group B2 with the following unit cell parameters: a = 69.59 A; b = 61.61 A; c = 56.11 A; gamma = 117.57 degrees. The X-ray data set to 1.7 A resolution has been collected on an automatic synchrotron (EMBL Hamburg Station).

Amino Acid Sequence↗

PubMed1997

[Affinity sorbents with tripeptide morpholine ligands for isolation of proteases].

New affine sorbents were synthesized involving tripeptide morpholides H-Ala-Ala-Leu-Mrp and H-D-Ala-Leu-Arg-Mrp as ligands that mimic substrates of subtilisin-like proteases and kallikrein, respectively. These were used for the isolation and purification of several proteases: trypsin, pepsin, alpha-chymotrypsin, thrombin, kallikrein, and termitase and were also efficient in the isolation of proteolytic enzymes from complex mixtures, such as the urine of children suffering from glomerulonephritis, hepatopancreas of Kamchatka crab, and dandelion roots. The ligands are competitive inhibitors of a number of proteases, and therefore, they were supposed to interact with the substrate binding sites in these enzymes.

Animals↗

PubMed1996

Fluorogenic peptide substrates for assay of aspartyl proteinases.

Via a combination of chemical and enzymatic synthesis, new hexapeptide substrates convenient for use in activity assessment of several aspartyl proteinases--porcine pepsin, human pepsin, gastricsin, and cathepsin D--were prepared. These peptide derivatives, o-aminobenzoyl-Ala-Ala-Phe-Phe-Ala-Ala-p-nitroanilide and N-(o-aminobenzoyl-Ala-Ala-Phe-Phe-Ala-Ala)-N'-2,4-dinitrophenyl ethylenediamine, contain a fluorescent o-aminobenzoyl moiety as well as p-nitroaniline or N-2,4-dinitrophenyl ethylenediamine--the groups that cause fluorescence quenching. Aspartyl proteinases hydrolyze the Phe-Phe peptide bond in the substrates, which diminishes quenching due to separation of the fluorescent and quenching moieties and leads to an increase in the fluorescence intensity of o-aminobenzoyl residue. Abz-Ala-Ala-Phe-Phe-Ala-Ala-Ded, being fairly well hydrolyzed by HIV proteinase, might be used for assay of this enzyme.

Amino Acid Sequence↗

PubMed1996

Buffalo (Bos buffali L.) chymosin purification and properties.

Buffalo chymosin was isolated from abomasum mucosa extract of buffalo calves by affinity chromatography on gramicidin S-agarose followed by ion exchange chromatography on gamma-aminopropylsilochrom. Its molecular weight, 36 +/- 1 kDa, is similar to that of bovine calf chymosin. The N-terminal sequence Gly-Glu-Val-Ala-Ser-Val-Pro- coincides with that of bovine enzyme, whereas some differences were found in the amino acid composition of these enzymes. Buffalo and bovine enzyme possess similar but not identical structures. General proteolytic and milk-clotting activities of buffalo chymosin are also similar to those of bovine proteinase. pH-Optimum of its activity against hemoglobin lies at pH 4.0, somewhat higher than that for bovine chymosin, which indicates subtle differences in the functional properties of two enzymes.

Amino Acid Sequence↗

PubMed1996

[Proteolytic enzymes from Streptomyces fradiae: a metalloendopeptidase, subtilisin-like, and trypsin-like proteinases].

Three proteolytic enzymes-the metalloproteinase, SFMP, and two serine proteinases, SFSP and SFTP-have been isolated and purified from the culture fluid of Streptomyces fradiae using chromatography on bacitracin-silochrome, bacitracin-Sepharose, DEAE-cellulose and fractionation by ammonium sulfate. Study of physico-chemical and functional properties of the enzymes and structural analysis revealed that SFMP is a cysteine-containing metalloendopeptidase with M(r) of 36 kDa, has a peak activity for synthetic substrates at pH 7.0-7.5 and at 60-65 degrees C and is stable at pH 7.0-9.0. The serine proteinase SFSP is related to subtilisin-like enzymes, has a M(r) of 29 kDa and a pH optimum at 7.5-8.5 at temperature up to 50 degrees C. The proteinase is stable at pH 4.0-9.0 and retains 30% of its activity at 70 degrees C. The other serine proteinase, SFTP, has a M(r) of 26 kDa and is related to trypsin-like enzymes. Its activity for synthetic substrates of trypsin is maximal at pH 6.8-8.8 at 50 degrees C. The enzyme is stable at pH 4.5-8.5 and at temperature below 50 degrees C. It has been shown that Streptomyces fradiae, like Streptomyces griseus and other Streptomycetes, possesses an ability to secrete serine proteinases (SFSP and SFTP) related to two evolutionally distinct families of serine proteinases, i.e., subtilisin and chymotrypsin families. SFMP and SFSP have been isolated and characterized for the first time.

Amino Acid Sequence↗

PubMed1996

[Bacillus cereus chitinases: isolation and characteristics].

Three chitinases (M(r) = 68, 52 and 38 kDa) have been isolated from the cultural filtrate of Bacillus cereus strain VKPM B-6838 by stepwise hydrophobic chromatography on butyl-Toyopearl and gel filtration on Superdex 75 (FPLC). The chitinases are stable in the pH range 4-10 and have the same pH optimum of activity. The 68 and 38 kDa enzymes display the highest activity at 60 degrees C. while the 52 kDa chitinase-at 50 degrees C. In contrast with the 68- and 52 kDa enzymes, the 38 kDa chitinase hydrolyzes not only colloidal but also "crystalline" chitin and chitosan. None of the chitinases hydrolyzes chitobiose. The N-terminal sequences (10 amino acids) of the 52 and 38 kDa chitinases do not reveal structural similarity between themselves or to other known bacterial chitinases. The 68 kDa chitinase is not immunologically related to the 52 and 38 kDa enzymes. The results obtained suggest that the 68, 52 and 38 kDa chitinase are the unique proteins.

Amino Acid Sequence↗

PubMed1996

[Sequential attachment of arginine residues to peptides catalyzed by subtilisin. II. Effect of the nature of acylating and nucleophilic components and small amounts of water in organic solvents].

The reaction of Dnp(or Z)-Ala2-Xaa-OCH3 (Xaa = Ile of Val) with arginine amide or p-nitroanilide was studied in organic solvents, which was catalyzed by subtilisin sorbed on macroporous glass, It resulted in the formation of peptides containing one to four arginine residues: Dnp(or Z)-Ala2-Xaa-(Arg) 1-4-NH2. The number of arginine residues attached to the peptide depended on the water content in organic solvents, nature of the amino acid residue Xaa in the P1 position of the acylating component, and the type of the N-protective group. The reaction can be used for synthesizing arginine-containing substrates of convertases and cathepsins B, L, and O. A chromogenic substrate for duodenase Z-Ala2-Ile-Arg2-pNA was obtained.

Acylation↗

PubMed1996

[Sequential attachment of arginine residues to peptides, catalyzed by subtilisin. 1. Effect of organic solvent composition].

Subtilisin 72 sorbed on a macroporous glass catalyzed the condensation of Dnp(or Z)-Ala2-Leu-OCH3 with arginine amide in a mixture of DMSO and acetonitrile at a water content less than 0.07% (v/v). This reaction resulted in the sequential formation of peptides containing from one to four C-terminal arginine residues. The number of attached Arg residues depended on the DMSO concentration in the solvent mixture, which determined the local arginine excess on the sorbent surface, which significantly exceeded the molar arginine excess in the solution. This enzymic reaction opened up new opportunities for preparation of peptides with different content of arginine residues.

Arginine↗

PubMed1996

[Isolation and properties of serine proteinase PC from the Kamchatka crab, Paralithodes camtschatica--a proteolytic enzyme with broad specificity].

A homogeneous serine proteinase PC has been isolated from the Camchatka crab (Paralithodes camtschatica) hepatopancreas using affinity chromatography on arginine-Sepharose, protamine tryptic peptide-agarose and ion-exchange chromatography on Mono-Q, with a 68% yield. The enzyme is completely inhibited by diisopropylfluorophosphate, a typical inhibitor for serine proteinases. The molecular mass of the proteinase is 29 kDa, pI is 3.0. The proteinase splits Glp-Phe-Ala-pNA optimally at pH 7.5 and 47-55 degrees C; Km is 0.83 mM, kcat is 67 s-1. The enzyme is stable at pH 4-9. Proteinase PC possesses a broad substrate specificity and splits the peptide bonds formed by the carboxyl group of hydrophobic amino acids, arginine and lysine, in peptides and proteins. The enzyme hydrolyzes fibrin and collagen. Its N-terminal sequence, IVGGQEATP, reveals a 90% homology with analogous sequences of collagenolytic proteinases from other crab species.

Amino Acid Sequence↗

PubMed1995

Macluralisin--a serine proteinase from fruits of Maclura pomifera (Raf.) Schneid.

A serine proteinase was isolated from fruits of Maclura pomifera (Raf.) Schneid. by affinity chromatography on bacitracin-containing sorbents and gel-filtration. The enzyme, named macluralisin, is a glycoprotein with a molecular mass of 65 kDa; its protein moiety corresponds to a molecular mass of 50 kDa. The substrate specificity of macluralisin towards synthetic peptides and insulin B-chain is similar to that of cucumisin, a subtilisin-like proteinase from melon fruit. The enzyme is completely inhibited by diisopropylfluorophosphate. Its amino-acid composition resembles that of a serine proteinase isolated from the Cucurbitaceae. The N-terminal sequence has 33% of its residues identical to those of the sequence of fungal subtilisin-like proteinase K. Hence, Maclura pomifera serine proteinase belongs to the subtilisin family, which seems to be broadly distributed in the plant kingdom.

Amino Acid Sequence↗

PubMed1995

Domain organization of Bacillus thuringiensis CryIIIA delta-endotoxin studied by denaturation in guanidine hydrochloride solutions and limited proteolysis.

Denaturation of Bacillus thuringiensis CryIIIA delta-endotoxin--an insecticidal protein, active against Coleoptera larvae--in concentrated guanidine hydrochloride solutions was pursued by fluorescence and circular dichroism spectroscopy and limited proteolysis. It was found that the protein consists of two fragments that differ by their stability to denaturation by guanidine hydrochloride at pH 3. The less stable fragment corresponds to the N-terminal alpha-helical domain limited by Leu-279; the more stable one starts with Ile-280, contains about 330 amino acid residues, and corresponds to the molecule C-terminal moiety that consist of its two beta-structural domains forming a superdomain.

Amino Acid Sequence↗

PubMed1995

Carboxypeptidase T.

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Amino Acid Sequence↗

PubMed1995

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. Subtilisin 72 is especially effective as a catalyst for the acylation of p-nitroanilides by N-protected tripeptide methyl esters--the derivatives capable of occupying the S1, S2 and S3 subsites of its extended binding site. Even dipeptide esters with D-amino acids in P2 position can be applied for p-nitroanilide acylation. The efficiency of alpha-chymotrypsin as a catalyst for peptide synthesis is more limited due to restricted specificity of this enzyme.

Amino Acid Sequence↗

PubMed1995

[Enzymatic synthesis of peptides of arginine-chromophore substrates of metalloproteinases and carboxypeptidases].

Subtilisin 72 sorbed on the surface of macroporous glass catalyzes a condensation of the esters of N-acylated peptides with arginine derivatives in organic solvents. The sorbed enzyme can be used repeatedly, which makes it possible to synthesize the chromophore substrates of metalloproteinases and carbopeptidases of the general formula Dnp-Ala-Ala-Xaa-Arg-NH2 (Xaa = Leu, Phe, Val, Ile). In tetrapeptides, metalloproteinases hydrolyze the Ala-Xaa bond with the removal of Dnp-Ala-Ala-OH, which can be determined spectrophotometrically. The chromophore substrates of carboxypeptidases of the B type (Dnp-Ala-Ala-Xaa-Arg-OH and Dnp-Ala-Ala-Arg-OH) are obtained by hydrolysis of the corresponding amides by trypsin.

Amino Acid Sequence↗

PubMed1995

[Isolation and properties of carboxypeptidase from the Kamchatka crab Paralithodes camtshatica].

Homogeneous carboxypeptidase PC from a hematopancreas of kamchatka crab Paralithodes camtshatica was obtained by means of an affinity chromatography on sorbents containing arginine, protamine hydrolysate, and phenylalanine as ligands with an yield 23% and purification degree 37.4. The isolated enzyme has a molecular mass 34 kDa, as evidenced by an SDS-PAGE; pI 3.1; an optimum pH 6.5, as estimated for hydrolysis of Dnp-Ala-Ala-Arg; pH-stability range 5-8 in the presence of Ca2+; a temperature optimum 55 degrees C; and Km 0.4 mM. The carboxypeptidase is activated by Co2+ and Ca2+ ions and is inhibited by EDTA and o-phenanthroline, and therefore, it is a metallocarboxypeptidase. The enzyme can effectively split off C-terminal residues Phe and Tyr, as well as Arg and Lys. Residues Pro, Glu, and Asp cannot be split off, and they stop the cleaving of a preceding bond. Thus, the carboxypeptidase PC of kamchatka crab has a mixed substrate specificity, which is characteristic of carboxypeptidase from crawfish and of microbial carboxypeptidases T and SG. The new carboxypeptidase has an amino acid composition Asp41Thr24Ser22Glu32Pro15Gly32Ala291/2Cys5Val19Met8Ile14Leu20Ty r18Phe8Lys7His4 Arg8Trp4. The N-terminal sequence of the enzyme demonstrate a 40% homology with the N-terminal sequence of carboxypeptidase from crawfish.

Amino Acid Sequence↗

PubMed1994

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. The solvent consisted of acetonitrile, dimethylformamide (DMF), and 4% (v/v) of water. The DMF/acetonitrile ratio was varied between 0 and 1/1. At high concentration of the acyl-group donor and approximately equimolar ratio of the nucleophile and the acyl-group donor, quantitative formation of MalAlaAlaPheXaaNH2 or ZAlaAlaPheXaaNH2 occurred. As a result, a method for the synthesis of polypeptide amides was developed. At low concentration of the acyl-group donor and excess of the nucleophile, the condensation by-products with two and three nucleophile molecules were found in the reaction mixtures. The data obtained provided evidence that organic solvents affected the S'1-specificity of alpha-chymotrypsin and the S1-specificity of subtilisin 72, while the S1-specificity of alpha-chymotrypsin and the S'1-specificity of subtilisin 72 were not affected. When the DMF content was increased, the rate of the alpha-chymotrypsin-catalyzed reactions decreased. In contrast to this, an increase in DMF content accelerated the subtilisin 72-catalyzed reactions. Hydrolysis of the acyl-group donor did not occur in the alpha-chymotrypsin-catalyzed reactions. Significant (up to 50%) formation of MalAlaAlaPheOH was observed at the early stage of the subtilisin 72-catalyzed reactions. Later MalAlaAlaPheOH underwent synthesis.

Amino Acid Sequence↗

PubMed1994

Production of multiple delta-endotoxins by Bacillus thuringiensis: delta-endotoxins produced by strains of the subspecies galleriae and wuhanensis.

A method was developed to assess the number of delta-endotoxins contained in Bacillus thuringiensis entomocidal crystals. It utilized proteolytic conversion of 130-kDa protoxin into 60- to 65-kDa "true" toxin via limited proteolysis with trypsin and separation of stable N-terminal domains by fast-performance liquid chromatography. Immunodiffusion experiments and N-terminal sequence determination (applied to the major component isolated by SDS-PAGE) completed the analysis of the crystal protein composition. The application of this approach to crystals produced by cells of B. thuringiensis subsp. galleriae and wuhanensis allowed us to identify at least seven and eight different delta-endotoxins, respectively. Among those delta-endotoxins assigned to previously described families, CryIA, CryID, CryIF, and CryIG were found, as well as crystal proteins, which possess N-terminal amino acid sequences very different from those of all known delta-endotoxins. Possible functional consequences of delta-endotoxin multiplicity are discussed.

Amino Acid Sequence↗