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Biomedical subjects

V Turk

Publications and source records attributed to V Turk.

At least 199 records · Page 11Linked to original sources
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↗
PubMed1986

Proteinases of various Claviceps purpurea strains.

Extra- and intracellular proteinases from various Claviceps purpurea strains grown in submerged culture have been studied. A maximum level of intracellular proteinases was observed on the 6th day of culture growth, whereas extracellular activity continued to increase throughout the culture growth. Proteinases were purified and characterized. The ergotamine strain secreted one aspartic and two serine proteinases, whereas from the disrupted mycelium only the aspartic proteinase could be isolated. The ergocornine strain secreted the aspartic proteinase in two forms and the ergocristine strain produced an aspartic and a serine proteinase.

Claviceps↗
PubMed1985

Human leucocyte urokinase inhibitor--purification, characterization and comparative studies against different plasminogen activators.

A plasminogen activator inhibitor (PA-I) which inhibits primarily plasminogen activator of the urokinase type (u-PA) was isolated from the cytosol of human peripheral leukocytes. The inhibitor was isolated using ion exchange chromatography, gel filtration and FPLC. This inhibitor has an apparent molecular weight of 45 kDa, determined by SDS-PAGE, and a pI of 5.5-5.7. The inhibitor is a fast reacting inhibitor, is thermally unstable and is inactivated outside the pH range 7-9. Treatment of cytosol to pH 9 for 30 min at 37 degrees C resulted in a large increase in inhibitory activity. Antibodies against human placental UK-I completely quenched the inhibitory activity of human leucocyte UK-I.

Blood Proteins↗
PubMed1985

Genealogy of mammalian cysteine proteinase inhibitors. Common evolutionary origin of stefins, cystatins and kininogens.

A model for the evolution of mammalian cysteine proteinase inhibitors has been constructed on the basis of sequence homology. This model suggests that the diversity of cysteine proteinase inhibitors has evolved from two ancestral units forming the building blocks of stefin and cystatin. Gene triplication of the archetypal inhibitor generated the kininogen heavy chain which contains three cystatin-like copies. Hence, the superfamily of mammalian cysteine proteinase inhibitors is constituted by at least three distinct families, with stefin, cystatin and kininogen as their prototypes.

Amino Acid Sequence↗
PubMed1985

Cystatin, a protein inhibitor of cysteine proteases alters viral protein cleavages in infected human cells.

Chicken cystatin is a previously described small protein which has the property of inhibiting cysteine active site proteases. The protein, when added to cultured human cells, alters the intracellular proteolytic processing of poliovirus proteins, and causes a reduction in virus yield. It is suggested that the cystatin is able to penetrate to the cellular cytoplasm and inhibit the action of the poliovirus protease.

Animals↗
PubMed1985

Human plasma kininogens are identical with alpha-cysteine proteinase inhibitors. Evidence from immunological, enzymological and sequence data.

Human high- and low-Mr kininogens were shown to be potent inhibitors of cysteine proteinases such as cathepsin L and papain (Ki = 17-48 pM). A strong immunological cross-reaction between the kininogens and low-Mr alpha-cysteine proteinase inhibitor from human plasma was found. Comparison of partial amino acid sequences from high- and low-Mr kininogen and low-Mr alpha-cysteine proteinase inhibitor demonstrated sequence identity for all segments analyzed. These findings suggest that the kininogens and the alpha-cysteine proteinase inhibitors from human plasma are identical proteins.

Amino Acid Sequence↗
PubMed1985

Amino acid sequence of human liver cathepsin B.

The complete amino acid sequence of cathepsin B (EC 3.4.22.1) from human liver was determined. The 252-residue sequence was obtained by automated solid-phase Edman degradation of the light and heavy chain resulting from limited proteolysis of the single-chain enzyme and of fragments produced by cyanogen bromide and enzymatic cleavage of the heavy chain. Human liver cathepsin B has 83.7% identical residues with the corresponding enzyme from rat liver. Comparison of both mammalian cathepsin B sequences with the sequence of papain provides further evidence that lysosomal and plant cysteine proteinases have evolved from a common ancestor and share a similar catalytic mechanism.

Amino Acid Sequence↗
PubMed1985

Crystallization of chicken egg white cystatin, a low molecular weight protein inhibitor of cysteine proteinases, and preliminary X-ray diffraction data.

The shorter-chain form of chicken egg white cystatin has been crystallized in 1.6 M-phosphate buffer at pH 4.0 by vapour diffusion. The crystals are of trigonal space group P3121 (or P3221), have cell constants a = b = 47.9 A, c = 87.5 A, alpha = beta = 90 degrees, gamma = 120 degrees, and contain one molecule of 12,191 molecular weight per asymmetric unit. They diffract well to about 2.0 A resolution and are suitable for X-ray crystal structure analysis.

Animals↗
PubMed1984

Species variations amongst lysosomal cysteine proteinases.

Properties of cathepsin L from rat liver lysosomes were compared with those of a similar enzyme, cathepsin S from beef spleen. Major characteristics of cathepsin L are the high activity against Z-Phe-Arg-methylcoumarylamide and sensitivity to the fast reacting irreversible inhibitor Z-Phe-Phe-diazomethane. In contrast, cathepsin S hydrolyzes Z-Phe-Arg-methylcoumarylamide only slowly and Z-Phe-Phe-diazomethane cannot be regarded as a potent inhibitor of this enzyme. The differences in the substrate specificity of cathepsin L from rat liver and cathepsin S from beef spleen are discussed in comparison with the substrate specificity of cathepsin B from rat and human liver and beef spleen.

Animals↗
PubMed1984

Conformation, structure and activation of bovine cathepsin D. Unfolding and refolding studies.

Cathepsin D is found in the cell in two forms, one a single polypeptide chain (Mr 44 000) and the other a non-covalent complex of two peptides of Mr 14 000 and 30 000. These correspond to the N-terminal and C-terminal regions of the single chain from which they originate. It has been shown that the two forms of the enzyme are closely similar in secondary-structure content, in aromatic amino acid environment and in denaturation behaviour. The two-chain enzyme has half the specific activity of the single-chain form. The denaturation and renaturation of the single-chain cathepsin D has now been studied by c.d., fluorescence and enzyme activity. Activity is lost irreversibly on unfolding, but the loss of backbone ellipticity and of folded aromatic environment is 75% reversible. The enzyme unfolds in two main stages, and the kinetics of these transitions indicate the existence of at least two intermediate forms between the native and the fully unfolded states. A further form of the enzyme exists in 0.5 M-guanidinium chloride. It is characterized by having an activity 40% greater than that of the native state. This increase is not reversed on removing the denaturant. The similarities between cathepsin D and pepsin are discussed.

Animals↗
PubMed1984

Human cystatin, a new protein inhibitor of cysteine proteinases.

A new low-molecular weight protein inhibitor of cysteine proteinases, human cystatin, was isolated from sera of patients with autoimmune diseases. It inhibits papain, human cathepsin H and cathepsin B. According to its partially determined amino-acid sequence, human cystatin is highly homologous to egg white cystatin, but only distantly related to stefin, the cytosolic protein inhibitor of cysteine proteinases isolated from human polymorphonuclear granulocytes. Very probably human cystatin is identical with human gamma-trace, a microprotein of known sequence but hitherto unknown function.

Amino Acid Sequence↗
PubMed1983

Serine proteinase inhibitors from Vipera ammodytes venom. Isolation and kinetic studies.

Three protein inhibitors of serine proteinases were isolated from the crude venom of the long-nosed viper Vipera ammodytes ammodytes by ion-exchange and gel chromatography. Two of them strongly inhibit trypsin (Ki = 3.4 X 10(-10) and 5.6 X 10(-10) M), while the third one primarily inhibits chymotrypsin (Ki = 4.3 X 10(-9) M). Their Mr values are close to 7000, and pI is 9.8 in both trypsin inhibitors and 10.0 in the chymotrypsin inhibitor. The N-terminal group in the former inhibitors is blocked; arginine is the N-terminal amino acid in the latter. Besides trypsin and alpha-chymotrypsin, the trypsin inhibitors also inhibit plasmin, human plasma kallikrein and porcine pancreatic kallikrein. The chymotrypsin inhibitor inhibits trypsin and human plasma kallikrein only weakly and does not inhibit plasmin and porcine pancreatic kallikrein. According to their properties, all three inhibitors belong to the Kunitz-pancreatic trypsin inhibitor family of inhibitors.

Amino Acids↗
PubMed1983

Immunochemistry of leucocyte intracellular proteinase inhibitors.

The antiserum was raised in rabbits against intracellular inhibitors I-1, I-2 and I-3 isolated from the soluble phase of disrupted pig peripheral leucocytes. It was demonstrated with double immunodiffusion and with immunoelectrophoresis that the isolated inhibitors with different biochemical characteristics are three different, specific and unrelated proteins. With the techniques used, it was clearly confirmed that the inhibitors were isolated in a pure form and that they are located in cytoplasm and nucleus. The suppression of inhibitors by antiinhibitors antibodies was also demonstrated.

Animals↗
PubMed1983

Protein inhibitors of cysteine proteinases. I. Isolation and characterization of stefin, a cytosolic protein inhibitor of cysteine proteinases from human polymorphonuclear granulocytes.

A protein inhibitor of cysteine proteinases, "stefin", was purified from cytosol of human polymorphonuclear granulocytes. Affinity chromatography on carboxymethylated papain-Sepharose was used as the first step, followed by ion exchange chromatography on DEAE-Sephacel, which resolved four inhibitory peaks. The main peak, comprising approx. 80% of total inhibitory activity was characterized. It was found to be a homogenous protein with an apparent molecular mass slightly lower than that of cytochrome c and with an isoelectric point of 4.65. The inhibitor inhibits papain at a molar ratio of 1:1 as well as cathepsin B and H, but it does not inhibit serine and aspartic proteinases. It is stable at elevated temperature and in alkaline pH, but looses its activity in acid pH. Oxidized glutathione has no effect on its inhibitory activity.

Chromatography, Affinity↗