Enzymatic characterization and functional groups of polyphenol oxidase from the pupae of blowfly (Sarcophaga bullata).
Polyphenol oxidase (EC 1.14.18.1) 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, 30 degrees C). Activity was maximal at 40 degrees C, 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 micro M.
Wang
Qin
Q
Key Laboratory of Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen, 361005, China.
Chen
Qing-Xi
QX
Huang
Xiao-Hong
XH
Ke
Li-Na
LN
Shi
Yan
Y
Wang
Jun
J
D000818:Animals; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004175:Diptera / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D007700:Kinetics; D011679:Pupa / Q000201:enzymology*; D011794:Quercetin / Q000494:pharmacology; D013329:Structure-Activity Relationship
D011794:Quercetin; D004156:Catechol Oxidase