The present report deals with the investigation of the effect of 4-hydroxy-trans 2,3-nonenal (HNE), hexanal (HEX) and malondialdehyde (MDA), the major products of lipid peroxidation, on the glycosylation pathway of rat liver Golgi apparatus. Defined concentrations of the aldehydes were added to isolated fractions of formative (F3) and secretory (F1 + F2) Golgi compartments, then incubated at 37 degrees C for 10 min. At the end of the incubation the activity of galactosyl-(GT) and sialyl-(ST)transferases, the main enzymes of the terminal protein and lipoprotein glycosylation, was evaluated. A significant impairment of both these activities was observed with HNE and HEX but not with MDA. These data suggest that aldehydes generated during peroxidation reactions are able to impair the protein and lipoprotein maturation mechanism which is normally achieved through a complete glycosylation.
The role of ubiquinone in the Golgi apparatus is still unknown, even if it might be considered as a lipid marker of the Golgi compartment because of its high content in these subcellular fractions. In vivo modulation of ubiquinone with ethanol and in vitro pentane extraction show that ubiquinone is not required either for NADH-ferricyanide reductase, acetaldehyde dehydrogenase activity, or Ca2+ and Mg2+ stimulated ATPases. Since ubiquinone does not seem to be involved in these enzymic activities in Golgi compartments, other possible functions are discussed, related to a role in membrane fluidity or as a barrier to the propagation of free radicals.
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