title: A low-molecular-weight inhibitor of the neutral proteinase from rat intestinal smooth muscle.
abstract: 1. Rat intestinal smooth muscle was shown to contain endogenous inhibitory activity towards the neutral trypsin-like muscle proteinase described previously [Beynon & Kay (1978) Biochem. J. 173, 291--298]. 2. Comtamination of the muscle tissue by mucosal, blood and pancreatic inhibitors was shown to be unlikely. 3. The inhibitory activity was resolved into high- and low-molecular-weight components. 4. The low-molecular-weight component was purified to homogeneity. It has a molecular weight of approx. 9000 and was stable over the pH range 3--11. 5. It inhibited the muscle proteinase competitively (Ki congruent to t microM), but had no effect on any of the other proteinases tested. 6. Leupeptin also inhibited the muscle proteinase competitively (Ki congruent to 0.3 microM), whereas the low-molecular weight proteins gastrin, glucagon and insulin B-chain had very little effect. 7. A role for a weakly binding inhibitor in modulating the influence of the neutral proteinase on intracellular protein degradation is considered.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D007421:Intestine, Small; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors; D008297:Male; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000032:analysis*; D010455:Peptides / Q000494:pharmacology; D011480:Protease Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D011506:Proteins / Q000494:pharmacology; D051381:Rats
chemical_list: D000596:Amino Acids; D007976:Leupeptins; D010455:Peptides; D011480:Protease Inhibitors; D011506:Proteins; D008291:Malate Dehydrogenase