Restoration of Deoxycholate-Disrupted Membrane Oxidases of Micrococcus lysodeikticus1
AUTOR(ES)
Eisenberg, R. C.
RESUMO
Membrane-associated l-malate and reduced nicotinamide adenine dinucleotide (NADH) oxidase complexes of Micrococcus lysodeikticus were inactivated with deoxycholate. Reactivation of NADH oxidase by addition of Mg2+ occurred in these detergent-membrane mixtures, but reactivation of l-malate oxidase did not occur in the presence of deoxycholate. Removal of detergent by gel filtration allowed Mg2+-dependent restoration of both l-malate and NADH oxidases. Maximal NADH and l-malate oxidase restoration required 10 min and 40 min, respectively, at 30 mm MgSO4. Maximal restoration of both oxidases required at least 12 mm MgSO4 in an incubation period of 1 hr. Reduced-minus-oxidized difference spectra of Mg2+-restored membrane oxidases showed participation of cytochromes b, c, and a when either l-malate or NADH served as reductant; addition of dithionite did not increase the α- and β-region absorbancy maxima of these hemoproteins when restored membranes were first reduced with the physiological substrates l-malate or NADH. Not all divalent cations tested were equally effective for reactivation of both oxidases. l-Malate oxidase was restored by both Mn2+ and Ca2+. NADH oxidase was not activated by Mn2+ and only slightly stimulated by Ca2+. Separation of deoxycholate-disrupted membranes (detergent removed) into soluble and particulate fractions showed that both fractions were required for Mg2+-dependent oxidase activities. Electron micrographs indicated conditions of detergent treatment did not destroy the vesicular nature of protoplast ghost membranes.
