Characterization of variant forms of organophosphorus hydrolase

Abstract

Organophosphorus hydrolase (OPH) is an enzyme capable of degrading toxic organophosphorus chemicals including the chemical warfare agents, sarin and VX, as well as many insecticides. This project seeks to understand how structure contributes to the enzyme's activity and stability by identifying regions of the enzyme necessary for each. PCR mutagenesis was used to create 67 variant forms of the gene that encodes OPH. Eight variant genes were then sequenced to locate the mutations in the enzymes' structure. Two of the eight variants contained only silent mutations and expressed wild-type OPH protein. The mutations made in two of the variants prevented the protein from being expressed. Characterization of the enzymes relative to two substrates, paraoxon and demeton-S, indicated that six variants had severely decreased activity. Five of these variants contained mutations in regions that have previously been shown to affect the enzyme's activity. Only one variant, 12, contained a mutation in a novel region of the enzyme.