Enzymatic characterization and functional groups of polyphenol oxidase from the pupae of blowfly (Sarcophaga bullata)
Huang, XH（ Biocide Research Center, Fujian Agriculture and Forestry University）
- 生命科学－已发表论文 
Polyphenol oxidase (EC 18.104.22.168) was purified from the pupae of blowfly (Sarcophaga bullata) by a procedure involving ammonium sulfate fractionation and chromatography on DEAE-cellulose and Sephadex G-100. Kinetic characteristics of the enzyme were determined using L-DOPA as substrate. The specific activity of the enzyme was 770 U/mg, and the Michaelis constant (Km) was 1.5 +/- 0.1 mM (pH 6.8, 30degreesC). Activity was maximal at 40degreesC, pH 6.5. Chemical modification experiments demonstrated that cysteine and tryptophan residues are essential and arginine residues are not essential to the enzyme function. The enzyme is inhibited by quercetin with an IC50 of 0.20 +/- 0.06 mM. The inhibition is of competitive type, and the inhibition constant was determined to be 88 muM.
出处Biochemistry (Moscow), Vol. 69, No. 8, 2004, pp. 918 920. Translated from Biokhimiya, Vol. 69, No. 8, 2004, pp. 1129-1132.