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Biomedical subjects

V Turk

Publications and source records attributed to V Turk.

At least 181 records · Page 10Linked to original sources
PubMed1988

Proteolytic cleavage of human fibrinogen by cathepsin B.

Human fibrinogen was cleaved by human liver cathepsin B in vitro. The time course of the degradation was followed by SDS-PAGE. Using activated cathepsin B in a weight ratio of enzyme to fibrinogen of 1:100 a pH optimum of 6.0 was found at 37 degrees C. For the separation of the fibrinogen degradation products a reversed phase HPLC system was used. Fibrinogen was cleaved by cathepsin B at the C-terminal side of the A alpha-chain, partially also on its N-terminal side and at the N-terminal end of the B beta-chain.

Antibodies, Monoclonal↗
PubMed1988

Structural and immunological relationship between laminin and the cysteine proteinase inhibitor stefin.

A sequence analogy was found between the C-terminal region of the B1 chain of laminin (residues 1538-1639) and cysteine proteinase inhibitors, in particular the stefin group. The sequence analogous with cysteine proteinase inhibitors occurs in fragment E8 obtained by elastase digestion of laminin. Antibodies raised against E 8 reacted with stefin but not with kininogen or cystatin.

Amino Acid Sequence↗
PubMed1988

Structural analogies between adhesive proteins and cysteine proteinase inhibitors.

Structural analogies were found between adhesive proteins, fibronectin and laminin, and a group of cysteine proteinase inhibitors. The sequences analogous with inhibitors occur in both adhesive molecules in the vicinity of their cell-binding sites: they comprise residues 1112-1212 in fibronectin and residues 1538-1639 of B1 chain in laminin. Both adhesive molecules display the highest degree of analogy with stefin-type inhibitors. The structural analogies also exist between fibronectin, laminin and P21, the c-Ha-ras gene protein produced by Escherichia coli.

Amino Acid Sequence↗
PubMed1988

Inhibitors of cysteine proteinases from potato.

Potato tubers contain considerable amounts of inhibitors of cysteine proteinases. The majority of inhibitory activity is due to low-molecular mass inhibitors differing in isoelectric points. Three of them were obtained in homogenous form, namely PCPIs (potato cysteine proteinase inhibitors) 6.6 (Mr 25,000), 8.3 and 9.4 (both Mr 22,000). They all appeared to be single-chain proteins. The amino-acid composition and the N-terminal amino-acid sequences show that at least two of them are homologous proteins, but so far no homology to the inhibitors of the cystatin super-family or to any other sequenced potato proteins is apparent. PCPIs inhibit papain and human cathepsins B, H, and L. The inhibitors interact with enzymes in apparently equimolar fashion, the interaction is of the tight binding type with Ki values ranging from 10(-6)M to 10(-11)M.

Amino Acid Sequence↗
PubMed1988

Human cathepsin B and cysteine proteinase inhibitors (CPIs) in inflammatory and metabolic joint diseases.

Synovial fluid of patients with different inflammatory and metabolic joint diseases contains low-molecular CPIs (stefins and cystatins) and high-molecular CPIs (kininogens). An additional inhibitory fragment with a molecular mass of about 20 kDa, which is a part of the kininogen molecule, has been detected. Cathepsin B and cystatin C were determined by ELISA test in 47 patients with rheumatoid arthritis, seronegative spondylarthritis, osteoarthritis, undifferentiated arthritis and gout. A significantly higher amount of cathepsin B was found in patients with rheumatoid arthritis. The elevation of cathepsin B was accompanied by an increased amount of cystatin C.

Amino Acid Sequence↗
PubMed1987

Collagenolytic cathepsins of rabbit spleen: a kinetic analysis of collagen degradation and inhibition by chicken cystatin.

We have investigated the steady state kinetics of the degradation of native fibrillar collagen at pH 3.4 by four collagenolytic cathepsins of rabbit spleen. For each enzyme, the dependence of initial velocity on collagen concentration was well described by the Michaelis-Menten mechanism. Km, expressed as the concentration of triple-helical chains, and kcat values were determined for cathepsins B, L, N and S. The ratio of Kcat to Km suggest that cathepsins L and N are far more effective at collagen solubilization than either cathepsins S or B. Ki values were determined for the inhibition of collagenolytic activity at pH 3.4 using cystatin, a naturally-occurring cysteine proteinase inhibitor. All four cysteine proteinases were inhibited by cystatin in this assay system, although it was found to be a tighter binding inhibitor of cathepsin L, than for cathepsins N and S (approximately 5-fold less), or cathepsin B (approximately 500-fold less).

Animals↗
PubMed1987

Alpha 2-macroglobulin in the sera of patients with periodontal disease.

The concentration of alpha 2-macroglobulin (alpha 2-M) in the sera of 86 blood donors was measured by laser nephelometry. Plaque index (PII), gingival index (GI) and probing depth were recorded around all existing teeth. All measured clinical parameters correlated positively with the concentration of alpha 2-M in the sera of the examined persons, but statistically significant positive correlation was found only in with the following: average gingival index and alpha 2-M concentration in the sera of females and average probing depth and alpha 2-M concentration in the sera of all examined females and males. This study supports the hypothesis that in long-standing chronic periodontal disease, the increased levels of proteinases might trigger the synthesis of alpha 2-macroglobulin in the host. The role of alpha 2-M as a proteinase scavenger and immunosuppressive agent is discussed briefly.

Adult↗
PubMed1987

Horse alpha 2-macroglobulin. Circular dichroism studies of conformational changes upon reaction with proteinases and methylamine.

The interaction of horse alpha 2-macroglobulin with methylamine, trypsin and cathepsin D was studied by circular dichroism in the far and near UV region, by polyacrylamide gel electrophoresis and by determination of its inhibitory activity. The CD spectra of horse alpha 2-macroglobulin resemble those of bovine und human alpha 2-macroglobulin. The CD spectra were changed in a different manner after the interaction of alpha 2-macroglobulin with methylamine, trypsin and inactive or active cathepsin D, indicating that more than one conformational change occurs. Cathepsin D activity was not affected by complex formation with horse alpha 2-macroglobulin. In contrast to the action of trypsin, treatment with methylamine did not increase the electrophoretic mobility of alpha 2-macroglobulin.

Animals↗
PubMed1987

Prediction of the secondary structures of stefins and cystatins, the low-molecular mass protein inhibitors of cysteine proteinases.

A procedure for classifying proteins of known sequence into structurally similar groups was developed on the basis of the Argos parametric approach. It is shown that stefins and cystatins constitute two structurally well resolved, but homologous groups of proteins. Furthermore, it is very probable that segments of secondary structures within each family are conserved, although significant differences between stefins and cystatins are indicated at the level of secondary structure. Next, secondary structures of all sequenced stefins and cystatins were predicted and used in the construction of secondary structures of the "typical stefin" and the "typical cystatin". Results were interpreted in the light of evolution and inhibition mechanism: Alignment of the "typical stefin" versus the "typical cystatin" secondary structure segments suggests that the divergence of stefin and cystatin families did not occur by a gene fusion event, but only by a mechanism of substitution, insertion and/or deletion. The central region of low-molecular mass cystatins, which is assumed to interact with cysteine proteinases, is predicted to be in a beta-sheet conformation. This resembles the beta-sheet in the active site of "standard mechanism" serine proteinases inhibitors.

Amino Acid Sequence↗
PubMed1986

Viral therapy: prospects for protease inhibitors.

Antiviral activities of known protease inhibitors were assayed in virus-infected cell cultures. Some members of the cystatin superfamily, in particular chicken cystatin, were able to block virus replication. In a binding assay, using purified components, chicken and human cystatin were able to bind poliovirus protease with affinities which were reflected in their relative antiviral potencies. Prospects for application of protease inhibitors in clinical viral infections are discussed.

Animals↗
PubMed1986

The effect of intracellular proteinases on transformation of human lymphocytes.

The effect of two intracellular proteinases, calf liver chymotrypsin-like neutral proteinase and human brain cathepsin H, and of two proteinase inhibitors, leupeptin and endogenous cysteine proteinases inhibitor, was studied on unstimulated and mitogen-stimulated peripheral human blood lymphocytes. Classification of blood samples into four types, on the basis of their potential for spontaneous and mitogen-stimulated transformation, helped in analyzing the results. Within some of these types, at least, there appears certain uniformity of response to proteinase action. Lymphocytes most susceptible to proteinase action were those that were insensitive to phytohemagglutinin mitogenic stimulus. The maximal effect of proteinases or their inhibitors was obtained most often when these agents were added to lymphocyte cultures 24 hours before mitogen. Both proteinases, although of quite different specificities, gave very often results of similar trend on the same lymphocyte culture. Moreover, this was followed also by the two inhibitors, which showed not only inhibitory, but also potentiating power of action on lymphocyte transformation. The regulatory nature of the action of proteinases within lymphocytes and other cells is underlined.

Animals↗
PubMed1986

Structural differences between rabbit cathepsin E and cathepsin D.

Rabbit cathepsins D and E were isolated from bone marrow. Both enzymes were purified by affinity chromatography on pepstatin-Sepharose 4B and Con A-Sepharose 4B. Purity of the enzymes was ascertained by two-dimensional gel electrophoresis after iodination. The isoelectric point of cathepsin D was found to be 6.95. Cathepsin E was shown to consist of two subunits having molecular masses each of 40 kDa and isoelectric points of 4.60 and 4.65, respectively. The amino-acid composition of cathepsin E was found to be different from that of cathepsin D.

Amino Acids↗
PubMed1986

Amino-acid sequence of ammodytoxin B partially reveals the location of the site of toxicity of ammodytoxins.

The complete amino-acid sequence of ammodytoxin B, a presynaptically toxic phospholipase A2 isolated from Vipera ammodytes ammodytes venom, was determined by manual and automated protein sequencing. Ammodytoxin B (i.v. LD50 = 0.58 mg/kg for white mice) is 30-fold less toxic than ammodytoxin A, the most toxic phospholipase isolated from the same venom. The two proteins (each 122 residues long) differ in only 3 residues located in positions 115, 118 and 119 (numbering according to R. Renetseder et al. (1985) J. Biol. Chem. 260, 11627-11634) suggesting that an exposed hydrophobic residue in position 115 and a basic residue in position 118 may be responsible for the increased toxicity of ammodytoxin A and should form at least one part of the site of toxicity in ammodytoxins.

Amino Acid Sequence↗
PubMed1986

Human cysteine proteinases and their protein inhibitors stefins, cystatins and kininogens.

The cathepsins B, H and L of human origin were isolated in pure form in sufficient quantities for structural characterization. The complete amino acid sequence of human liver cathepsin B was determined. Partial amino acid sequences of the human kidney cathepsin H and L show the highly conserved region around the active site cysteine. The cysteine proteinase inhibitors stefin A, human stefin B and human cystatin C were isolated, characterized and sequenced. Their amino acid sequences are compared with sequences of other protein inhibitors of the stefin and cystatin family, showing a high degree of homology throughout both families. The stefin and cystatin family, together with newly discovered kininogen family belong to the same superfamily of cystatins. The constructed dendrogram shows that the most closely related inhibitors so far sequenced are human stefin B and rat liver TPI.

Amino Acid Sequence↗
PubMed1986

Kininogens: inhibitors of cysteine proteinases in plasma and a similar inhibitor in chicken egg white.

Isolation, based on their inhibitory properties, is a fast and simple alternative method for the preparation of kininogens from human plasma. Pure native low Mr kininogen can be obtained in a much higher yield than with classical methods, provided that a similarly efficient inhibition of proteolysis is included. Chicken egg white also contains a high Mr inhibitor of cysteine proteinases. It closely resembles low Mr kininogen in its molecular weight, acidic isoelectric point and 1:2 inhibitor to enzyme molar binding ratio. Its relation to chicken serum kininogen is not known.

Animals↗