Purification and characterization of carboxylamidase from the fall armyworm, Spodoptera frugiperda (J. E. Smith)

Yu, S.J.; Nguyen, S.N.

Purification and characterization of carboxylamidase from the fall armyworm, Spodoptera frugiperda (J. E. Smith)

1998

Yu, S.J. | Nguyen, S.N.

Carboxylamidase which hydrolyzes p-nitroacetanilide was purified 256-fold from larval midguts of the fall armyworm, Spodoptera frugiperda (J. E. Smith), by ammonium sulfate fractionation, gel filtration, ion exchange chromatography, and hydroxyapatite chromatography. The purified enzyme was a monomer with a molecular weight of 59,000-60,000. The enzyme had an apparent K(m) value of 0.63 mM and a V(max) of 526.3 nmol/min/mg protein. It was inhibited by the hydrolase inhibitors paraoxon, triphenyl phosphate, eserine, and phenylmethylsulfonyl fluoride, showing I50 values of 4.7 micromolar, 0.2 mM, 16 micromolar, and 90 micromolar, respectively. The enzyme was also completely inhibited by the organophosphorus insecticides profenofos and dichlorvos at 0.1 mM. The enzyme was active toward other amides, such as acetanilide and phenacetin, and various alpha- and beta-naphtholic esters. Based on the purification factor, substrate specificity, and sensitivity to hydrolase inhibitors, the carboxylamidase appeared to be different from carboxylesterases in this insect.

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