The catalase activity of Nalpha-acetyl-microperoxidase-8.
Nalpha-Acetylated microperoxidase-8 (Ac-MP-8) is a water soluble, ferric heme model for peroxidases. We report here that Ac-MP-8 catalyzes catalase-type reaction in addition to peroxidase-type and cytochrome P450-type reactions. The catalase activity of Ac-MP-8 was determined by the Clark oxygen electrode, which measures the production of oxygen in solution. The Km and kcat of the decomposition of hydrogen peroxide (H2O2) catalyzed by Ac-MP-8 are 40.9 mm and 4.1 per s, respectively. The specificity constant (kcat/Km) of Ac-MP-8 in catalase-type reaction of H2O2 is 100.2,/m/s, which is 5- to 12- and 50- to 100-fold less than those of MPs in cytochrome P450-type reaction of aniline/H2O2 and peroxidase-type reaction of o-methoxyphenol/H2O2, respectively. These results indicate that Ac-MP-8 can catalyze three different types of reactions, and the relative catalytic specificities of Ac-MP-8 with a histidyl ligand exhibit the following orders: peroxidase-type > cytochrome P450-type > catalase-type reactions. Comparisons of the enzyme activities of Ac-MP-8 suggest that the fifth ligands of hemoproteins influence the ratio of the three types of reactions.
Department of Biochemistry and Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 701, Taiwan.
W-Y
WY
Jeng
Y-H
YH
Tsai
W-J
WJ
Chuang
D000107:Acetylation; D000595:Amino Acid Sequence; D002374:Catalase / Q000737:chemistry* / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism*
D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase; D002374:Catalase