Homocysteine promotes the LDL oxidase activity of ceruloplasmin.
Ceruloplasmin (CP) oxidises low density lipoprotein (LDL). The oxidising potential depends on the formation of Cu(+)-CP which is redox-cycled during oxidation. Homocysteine (HCY) reduces free Cu(2+), potentiating its cell-damaging property. We show that HCY enhanced LDL oxidation by CP, but did not activate the LDL oxidising potential of Cu(2+)-diamine oxidase. Selective removal of the redox-active Cu(2+) abolished the LDL oxidase activity of CP. However, HCY partially restored the LDL oxidase activity of redox-copper depleted CP, indicating that the remaining six copper atoms in CP may also be involved in the process. Spectroscopic and oxidation inhibition studies using the Cu(+)-reagent bathocuproine revealed that HCY induced Cu(+)-CP formation, thus promoting its LDL oxidase activity.
Exner
M
M
Department of Laboratory Medicine, University of Vienna, Vienna, Austria.
Hermann
M
M
Hofbauer
R
R
Hartmann
B
B
Kapiotis
S
S
Gmeiner
B
B
D002570:Ceruloplasmin / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism*; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry
D007202:Indicators and Reagents; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010618:Phenanthrolines; D006710:Homocysteine; C028559:bathocuproine sulfonate; D003300:Copper; D008715:Methionine; D002570:Ceruloplasmin; D003545:Cysteine