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.
Jeng
W-Y
WY
Department of Biochemistry and Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 701, Taiwan.
Tsai
Y-H
YH
Chuang
W-J
WJ
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