Chromophoric peptide substrates for activity determination of animal aspartic proteinases in the presence of their zymogens: a novel assay.
Solid-phase synthesis was used for the preparation of pyroglutamyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (I) and glycyl-glycyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (II), two water-soluble and sensitive chromophoric substrates of chicken pepsin, hog pepsin A, and bovine spleen cathepsin D. The kinetic constants of hydrolysis of the p-nitrophenylalanyl-phenylalanyl bond of the substrates were measured by difference spectrophotometry at 308 nm (delta epsilon = 860 M-1 cm-1) and by ninhydrin colorimetry (substrate I, epsilon 570 = 2.31 X 10(4) M-1 cm-1). The pH optimum of cleavage is 5 for the pepsins and 3.7 for cathepsin D. Since all three proteinases still have a significant activity at pH 5.5-6 a new, simple assay was designed for submicrogram quantities of pepsins in the presence of pepsinogens without interference of the latter. The method is particularly suitable for the analyses of the zymogen activation mixtures.
D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002402:Cathepsin D; D002403:Cathepsins / Q000378:metabolism; D002417:Cattle; D002645:Chickens; D002863:Chromogenic Compounds / Q000138:chemical synthesis; D010450:Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010434:Pepsin A / Q000378:metabolism; D010435:Pepsinogens / Q000378:metabolism; D013552:Swine
D002863:Chromogenic Compounds; D004792:Enzyme Precursors; D010435:Pepsinogens; D002403:Cathepsins; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; D010434:Pepsin A; D002402:Cathepsin D