Specificities of Subtilisin BPN' and Intracellular Proteinase from Bacillus Amyloliquefaciens in Reaction with Organophosphorus Inhibitors

The kinetics of irreversible inhibition of two proteinases from Bacillus amyloliquefaciens, i.e. an intracellular serine proteinase and subtilisin BPN', by O-n-alkyl-p-nitrophenyl methyl-phosphonates, (n-CnH2n+1O)(CH3)P(O)OC6H4NO2-p, n from 2 to 8, have been studied. The inhibitory activity of these compounds significantly depended upon the length of the alkoxy group in their acid moieties. The dependence of the second-order rate constant of the enzyme active site phosphorylation upon the Hansch hydrophobicity parameter π of the substituent -CnH2n+1 is described by the equation log ki = const. + φ, where φ is 1.1 for the intracellular proteinase and 0.7 for subtilisin BPN′. In subtilisin BPN′ the straight line holds up to n = 6, in the intracellular proteinase up to n = 5. The data point of a difference between the structures of nonpolar substrate-binding areas in the active sites of the two enzymes.