AN NADH-DEPENDENT DISULFIDE REDUCTASE-ACTIVITY IN THE ENDOPLASMIC-RETICULUM OF DICTYOSTELIUM-DISCOIDEUM

A novel disulfide reductase activity was observed in the amoeba, Dicty ostelium discoideum. Both 5,5'-dithiobis(2-nitro-benzoate) (DTNB) and insulin were substrates for reduction. NADH was utilized in preference to NADPH. The activity comigrated with NADPH-dependent cytochrome c r eductase on sucrose gradients, suggesting localization in the endoplas mic reticulum (ER). The buoyant density of the disulfide reductase was not shifted when ribosomes were released from the ER nor was the acti vity solubilized when membranes were shocked with low osmotic buffer. It therefore appears that the reductase was membrane-bound in the lume n of the smooth ER. (C) 1997 Academic Press.