Effect of urate on the lactoperoxidase catalyzed oxidation of adrenaline.
Lactoperoxidase is an iron containing enzyme, which is an essential component of the defense system of mammalian secretary fluids. The enzyme readily oxidizes adrenaline and other catecholamines to coloured aminochrome products. A Km-value of 1.21 mM and a catalytic constant (k = Vmax/[Enz]) of 15.5 x 10(3) min(-1) characterized the reaction between lactoperoxidase and adrenaline at pH 7.4. Urate was found to activate the enzyme catalyzed oxidation of adrenaline in a competitive manner, the effect decreasing with increasing adrenaline concentration. Lactoperoxidase was able to catalyze the oxidation of urate. However, urate was a much poorer substrate than adrenaline, and it seems unlikely that urate activates by functioning as a free, redox cycling intermediate between enzyme and adrenaline. The activation mechanism probably involves an urate-lactoperoxidase complex.
Løvstad
Rolf A
RA
Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway.
D000818:Animals; D002384:Catalysis; D004837:Epinephrine / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007784:Lactoperoxidase / Q000737:chemistry*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D013997:Time Factors; D014527:Uric Acid / Q000494:pharmacology*
D014527:Uric Acid; D007784:Lactoperoxidase; D010544:Peroxidases; D010100:Oxygen; D004837:Epinephrine