Inhibition of human elastase from polymorphonuclear leucocytes by gold sodium thiomalate and pentosan polysulfate (SP-54).
Human lysosoma) elastase, the serine proteinase from the azurophil granules of polymorphonuclear leucocytes, is inhibited by gold thiomalate and pentosan polysulfate (SP-54®). The kinetic mechanism of the inhibition was studied using succinyl-alanyl-alanyl-prolyl-valyl-4-methyl-7-coumarylamide and (t-butyloxycarbonyl-alanyl-p-nitrophenylester as subsrates. The degree of inhibition was also tested using insoluble elastin as substrate. Independent of the substrate, the maximal inhibition of elastase by gold thiomalate and pentosan polysulfate was 40% and 60%, respectively. Pentosan polysulfate behaved as a simple intersecting, hyperbolic, non-competitive inhibitor and k′i. the dissociation constant of the E-S-I complex, was 1.8 × 10−7M. The interaction between inhibitor and enzyme is driven by electrostatic forces. Gold thiomalate showed a hyperbolic mixed type inhibition (intersecting, slope-hyperbolic, intercept-hyperbolic, non-competitive inhibition) with k′i = 5.4 × 10−5M.
The overall kinetic mechanism of lysosomal elastase conforms to that of other serine proteinases. With both the ester and peptide substrates the rate limiting step of the reaction has been identified with the formation of the acyl-enzyme.