Orientation of Electron Transport Activities in the Membrane of Intact Glyoxysomes Isolated from Castor Bean Endosperm

Abstract

Intact glyoxysomes were isolated from castor bean endosperm on isometric Percoll gradients. The matrix enzyme, malate dehydrogenase, was 80% latent in the intact glyoxysomes. NADH:ferricyanide and NADH:cytochrome c reductase activities were measured in intact and deliberately broken organelles. The latencies of these redox activities were found to be about half the malate dehydrogenase latency. Incubation of intact orpnelles with trypsin eliminated NADH:cytochrome c reductase activity, but did not affect NADH:ferricyanide reductase activity. NADH oxidase and transhydrogenase activities were negligible in isolated glyoxysomes. Mersalyl and Cibacron blue 3GA were potent inhibitors of NADH:cytochrome c reductase. Quinacrine, Ca2", and Mg2" stimulated NADH:cytochrome c reductase activity in intact glyoxysomes. The data suggest that some electron donor sites are on the matrix side and some electron acceptor sites are on the cytosolic side of the membrane.

Evidence for the Presence of the Ascorbate-Glutathione Cycle in Mitochondria and Peroxisomes of Pea Leaves

“…This suggests that the MDHAR activity detected in this work in the matrix side of pea leaf peroxisomal membranes is the 32-kD membrane polypeptide previously characterized in the same membranes. It has been proposed that the trans-membrane protein MDHAR can oxidize NADH on the matrix side of the peroxisomal membrane and transfer the reducing equivalents as electrons to the acceptor monodehydroascorbate on the cytosolic side of the membrane (Luster and Donaldson, 1987;Bowditch and Donaldson, 1990). In this process molecular O, could also be an electron acceptor, with the concomitant formation of 0;-radicals (López-Huertas et al, 1996b).…”

“…The evidence reported in this work of the presente of APX and MDHAR in leaf peroxisomal membranes suggests a dual complementary function in peroxisomal metabolism of these membrane-bound antioxidant enzymes. The first function could be to reoxidize endogenous NADH to maintain a constant supply of NAD' for peroxisomal metabolism, an idea that was originally postulated for the membrane-bound NADH dehydrogenase of glyoxysomes from castor bean (Ricinus communis) endosperm (Fang et al, 1987;Luster and Donaldson, 1987;Bowditch and Donaldson, 1990). A second function of the membrane antioxidant enzymes could be protection against H,O, leaking out of peroxisomes.…”

The Activated Oxygen Role of Peroxisomes in Senescence1

“…The first function could be to reoxidize endogenous NADH to maintain a constant supply of NAD ϩ for peroxisomal metabolism (Fig. 3), an idea that was originally proposed for the membrane-bound NADH dehydrogenase of glyoxysomes from castor bean endosperm (Fang et al, 1987;Luster and Donaldson, 1987;Bowditch and Donaldson, 1990). A second function of the membrane antioxidant enzymes could be to protect against H 2 O 2 leaking from peroxisomes.…”

“…MDHAR was also localized in the peroxisomal membranes. It has been proposed that the trans-membrane protein MDHAR can oxidize NADH on the matrix side of the peroxisomal membrane and transfer the reducing equivalents as electrons to the acceptor monodehydroascorbate on the cytosolic side of the membrane (Luster and Donaldson, 1987;Bowditch and Donaldson, 1990). In this process, molecular O 2 could also act as an electron acceptor, with the concomitant formation of O 2 ⅐ Ϫ (Ló pez-Huertas et al , 1996).…”

Localization of donor and acceptor sites of NADH dehydrogenase activities using inside‐out and right‐side‐out plasma membrane vesicles from plants

“…c reductase activity, the NADH-cyt. bs reductase is widely used as a marker for the endoplasmic reticulum, however, in animal cells the activity is present in all endomembranes [l] and in plants it has been reported in glyoxysomes [23,24] and tonoplast [9]. In addition, both animal and plant PMs also possess this activity [1,3,10,1 l] (table l), possibly because endomembranes undergo active exchange with the PM ( [l] and references cited therein).…”