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Biomedical subjects

N M Schechter

Publications and source records attributed to N M Schechter.

62 records · Page 4Linked to original sources
PubMed1983

Human skin chymotryptic proteinase. Isolation and relation to cathepsin g and rat mast cell proteinase I.

A chymotrypsin-like proteinase was purified 2400-fold from human skin. The procedure involves extraction of the proteinase from skin in 2 M KCl, precipitation with protamine chloride, fractionation by gel filtration chromatography, and fractionation by chromatography using a CH-Sepharose-D-tryptophan methyl ester affinity column. The properties of this proteinase were compared to the rat mast cell proteinase I and human cathepsin G. Differences were observed in the rates at which the proteinases were inhibited by diisopropyl fluorophosphate, the sensitivity of the proteinases to protein proteolytic inhibitors, the relative hydrolytic rates of the proteinases for a series of substrates, and the kinetic constants of the proteinases for synthetic substrates. The human skin proteinase did not react with antiserum to the rat skin proteinase and did not elute in the same position as the rat skin proteinase on gel filtration columns. These data demonstrate that the human skin proteinase is distinct from the other proteinases. Extracts of involved skin from patients with cutaneous mastocytosis had 15-fold higher levels of chymotryptic activity than extracts of uninvolved skin or skin from normal controls. The enzymatic properties of the material extracted from the biopsied skin were similar to those of the proteinase from normal skin, suggesting that the human skin chymotrypsin-like proteinase is a mast cell constituent.

Animals↗
PubMed1982

Rapid conversion of angiotensin I to angiotensin II by neutrophil and mast cell proteinases.

Human neutrophil cathepsin G and human skin mast cell chymase rapidly convert angiotensin I to angiotensin II with only minor cleavage elsewhere in the molecule. The rate of cleavage is consistent with a potential role for either or both of these enzymes in an alternate pathway for angiotensin II synthesis. Since neither enzyme in inhibited by captopril, an angiotensin converting enzyme inactivator, it is possible that leukocyte and mast cell enzymes may play a significant role in the development of abnormally high local concentrations of angiotensin II, associated with various inflammatory processes.

Amino Acids↗
PubMed1976

Use of gel chromatography for the determination of the Stokes radii of proteins in the presence and absence of detergents. A reexamination.

In the course of a routine investigation of the complex between the erythrocyte membrane protein spectrin and sodium dodecyl sulfate, we observed a large discrepancy between the true Stokes radius (178 A, measured by hydrodynamic methods) and the apparent value derived from gel chromatography (107 A). In attempting to resolve this discrepancy, we have experiments that indicate that all large asymmetric particles may be subject to a similar discrepancy; e.g., native fibrinogne has a true Strokes radius of 108 A, whereas the value derived by column chromatography after calibration with globular proteins is only 71 A. The simplest interpretation is that end-on insertion of asymmetric particles into the gel pores contributes to their retardation. The phenomenon clearly limits the usefulness of gel chromatography as a quantitative measure of the hydrodynamic Stokes radius. Incidental data obtained in the course of this work indicate that spherical viruses may have weak chemical affinity for the porous gel. Chromatography of large proteins in the presence of detergents produced no effects ascribable to absorption of the detergents, but the results suggest a need for further study of possible interaction between detergents and small gel pores.

Chemical Phenomena↗
PubMed1976

Erythrocyte spectrin. Purification in deoxycholate and preliminary characterization.

Erythrocyte spectrin, isolated by aqueous extraction of erythrocyte ghosts, may be freed from contaminating membrane lipids and small amounts of other proteins by gel chromatography in 5 or 10 mM deoxycholate. The purified protein, in deoxycholate, is a mixture of monomers and dimers, both highly asymmetric molecules. The hydrodynamic properties of the dimer closely resemble those of muscle myosin, and spectrin and myosin also have similar circular dichroism spectra. The proportion of dimer to monomer in the purified protein varies from one preparation to another, an observation for which there is no simple explanation. In the absence of deoxycholate, spectrin associated beyond the dimer stage, possibly by loose end-to-end aggregation involving hydrophobic forces.

Binding Sites↗