Study of ceruloplasmin oxidase activity. The effect of pH.
To find out the mechanism of ceruloplasmin (CP) oxidase activity CP interaction with organic substrates adrenaline (AD), catechol, p-phenylenediamine) and Fe2+ was investigated. CP was shown to interact with the above substrates according to the Theorell-Chance mechanism to form a kinetically insignificant ternary complex. The oxygen molecule binds first to CP followed by the molecule of electron donor: the inhibition of enzymatic oxidation by the reaction product is competitive. The effects of pH on kinetic parameters (Ksm, Vs) of oxidation reactions of AD and Fe2+ in the presence of CP were examined. AD was shown to be able to bind both to the protonated and to the non-protonated form of CP whereas Fe2+ interacts only with the protonated form: the rate of catalytic event (Vs) is influenced by pH in the presence of AD whereas in the presence of Fe2+ only binding to CP (Ksm) is affected by pH. Kinetic schemes describing the order of binding of hydrogen ions in the course of above reactions are proposed.
Saenko
E L
EL
A.N. Bach Institute of Biochemistry, USSR Academy of Sciences, Moscow.
Siverina
O B
OB
Basevich
V V
VV
Yaropolov
A I
AI
D001667:Binding, Competitive; D002396:Catechols / Q000378:metabolism; D002570:Ceruloplasmin / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D004837:Epinephrine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D010084:Oxidation-Reduction; D010655:Phenylenediamines / Q000378:metabolism
D002396:Catechols; D010655:Phenylenediamines; D007501:Iron; D002570:Ceruloplasmin; C034221:catechol; C029728:4-phenylenediamine; D004837:Epinephrine