Monoascorbate free radical-dependent oxidation-reduction reactions of liver Golgi apparatus membranes.
Golgi apparatus from rat liver contain an ascorbate free radical oxidoreductase that oxidizes NADH at neutral pH with monodehydroascorbate as acceptor to generate a membrane potential. At pH 5.0, the reverse reaction occurs from NAD(+). The electron spin resonance signal of the ascorbate-free radical and its disappearance upon the addition of NADH (pH 7) or NAD(+) (pH 5.0) confirms monodehydroascorbate involvement. Location of monodehydroascorbate both external to and within Golgi apparatus compartments is suggested from energization provided by inward or outward flux of electrons across the Golgi apparatus membranes. The isolated membranes are sealed, oriented cytoplasmic side out and impermeable to NAD(+) and ascorbate. NAD(+) derived through the action of Golgi apparatus beta-NADP phosphohydrolase is simultaneously reduced to NADH with monodehydroascorbate present. The response of the NADH- (NAD(+)-) ascorbate free radical oxidoreductase system to pH in Golgi apparatus provides a simple regulatory mechanism to control vesicle acidification.
Navas
Placido
P
Universidad Pablo de Olavide-CSIC and CIBERER Instituto de Salud Carlos III, Centro Andaluz de Biologia del Desarrolo, Sevilla, E-4103, Spain.
Sun
Iris
I
Crane
Frederick L
FL
Morré
Dorothy M
DM
Morré
D James
DJ
D000818:Animals; D003683:Dehydroascorbic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006056:Golgi Apparatus / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats
C000820:semidehydroascorbic acid; D009247:NADH, NADPH Oxidoreductases; D003683:Dehydroascorbic Acid