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G Kalnitsky

Publications and source records attributed to G Kalnitsky.

18 recordsLinked to original sources
PubMed1986

The specificity of rabbit lung cathepsin I on biopeptides.

Ten peptides were tested as substrates for cathepsin I. The enzyme exerted both endopeptidase and aminopeptidase activities on 5 substrates, only aminopeptidase activity on 3 others, and only endopeptidase cleavage on one compound. One peptide was not significantly hydrolyzed. Aminopeptidase activity stopped one residue before a proline residue and endopeptidase cleavage took place one residue after a proline residue. With these substrates, this enzyme appears to have a broad specificity in its aminopeptidase action. However, cathepsin I appears to have a much narrower and more specific endopeptidase activity, hydrolyzing peptide bonds involving the nitrogen of branched chain or bulky or hydrophobic amino acids. Finally, some differences in the physical, chemical and biological properties of cathepsins H and I were discussed.

Amino Acid Sequence↗
PubMed1983

Properties of dipeptidyl peptidase I from rabbit (Oryctolagus cuniculus) lungs.

Dipeptidyl peptidase 1 (DAP I; EC 3.4.14.1) was isolated from rabbit lungs and purified to apparent homogeneity. Similarly as the liver and spleen enzymes, it requires Cl- ions for its activity and is activated by thiol compounds. With Gly-Arg-2-naphthylamide as a substrate the broad pH optimum for DAP I activity ranged from 5.0 to 6.5; at pH 6.0-9.0 the enzyme catalysed the transamidation reaction. The Arrhenius plot for the DAP I activity at pH 5.0 was inflected at a point corresponding to 28 C. The enzyme was inhibited by the protease inhibitors, N alpha-tosyl-L-lysylchloromethane, N-tosyl-L-phenylalanylchloromethane, phenylmethylsulphonyl fluoride and antipain. Molecular weight of DAP I determined by sedimentation equilibrium in the presence of substrate was 128 000; in the absence of substrate two molecular forms of Mr of 135 000 and 91 600 were revealed. The Mr value determined on Sephadex G-200 was 154 000 +/- 7000. Molecular weight of the subunits determined by the two methods was about 21 000. Association of subunits over the pH range 4.6-6.0 was favoured by lowered temperature (7 C), presence of the substrate and increased enzyme concentration in the presence of the substrate. Only the forms of higher molecular weight, probably hexamers and octamers, exhibited enzymatic activity.

Animals↗
PubMed1981

Muscle ribosome detachment factor. Does it have a role in the pathogenesis of Duchenne muscular dystrophy?

A protein that detaches ribosomes from rough microsomal membranes ("detachment factor") (DF) was isolated from the cytosol fraction of rat and human muscle. The procedure of isolation included differential centrifugation, precipitation with ammonium sulfate and column chromatography with Sephadex G-100. The protein which is not completely homogenous, has a molecular weight of 50,000-60,000 daltons, is heat labile and has an optimum pH at 7.4-7.6. The DF activity of the protein is inhibited by soybean trypsin inhibitor (73%), pepstatin (67%), and leupeptin (42%), although no proteolysis could be measured. The DF activity was tested on muscle samples (rough microsomal membranes) obtained from Duchenne muscular dystrophy (DMD) patients (7 cases) and normal controls (16 cases). The yield of membrane bound ribosomes (MBR) obtained from muscle samples of DMD patients by extraction with DF is 5-fold higher than from muscle samples of normal controls. The difference in MBR yield is not related to the type of DF. Similar values for MBR were obtained with rat and human (normal and dystrophic) DF. Ribosomal protein synthesis (RPS) with ribosomes extracted by DF showed values similar to the RPS of detergent extracted ribosomes. Our findings suggest the observed increase in membrane bound ribosomes in DMD probably results from increased levels of mRNAs coding for membrane and secretory proteins such as collagen.

Amino Acids↗