* To whom correspondence should be addressed.
Received January 27, 2005; Revision received February 22, 2005
The catalytic properties of organophosphate hydrolase (OPH) containing a hexahistidine tag His6 (His6-OPH) and purified to 98% homogeneity were investigated. The pH optimum of enzymatic activity and isoelectric point of His6-OPH, which were shown to be 10.5 and 8.5, respectively, are shifted to the alkaline range as compared to the same parameters of the native OPH. The recombinant enzyme possessed improved catalytic activity towards S-containing substrates: the catalytic efficiency of methylparathion hydrolysis by His6-OPH is 4.2*106 M-1*sec-1, whereas by native OPH it is 3.5*105 M-1*sec-1.
KEY WORDS: organophosphate hydrolase, fusion proteins, hexahistidine tag, organophosphate neurotoxins, substrate specificity