Gastric microsomal NADH-cytochrome b5 reductase: characterization and solubilization.
NADH-cytochrome b5 reductase from hog gastric microsomes was studied with respect to substrate dependence, optimum pH, thermal denaturation as well as anti-cytochrome b5 antibodies and different ions. The reduction of potassium ferricyanide by the enzyme was specific for NADH. Using potassium ferricyanide or trypsin-solubilized liver cytochrome b5 (Tb5) as substrates, enzyme activity was inhibited by ADP and to a lesser extent by ATP. Tb5- (but not ferricyanide-) reductase was activated by ionic strength up to 0.05 ion equivalent per liter and inhibited at higher strengths whatever the ion used (Cl-, Na+, Ca2+, Mg2+). Enzyme solubilization occurred with Triton X100. The solubilization increased the Tb5- (but not the ferricyanide-) reductase activity up to a Triton:protein ratio of 15. We therefore suggest that gastric microsomes contain a Triton soluble membrane-bound NADH cytochrome b5 reductase which is in many respects similar to the liver and red cell enzymes.
D000818:Animals; D003579:Cytochrome Reductases / Q000302:isolation & purification / Q000378:metabolism; D042966:Cytochrome-B(5) Reductase; D005292:Ferricyanides; D008861:Microsomes / Q000201:enzymology; D017830:Octoxynol; D011092:Polyethylene Glycols; D012995:Solubility; D013270:Stomach / Q000201:enzymology*; D013379:Substrate Specificity; D013552:Swine
D005292:Ferricyanides; D011092:Polyethylene Glycols; D017830:Octoxynol; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; C028033:potassium ferricyanide