The properties and behavior of a “microsomal” (100,000 X g particles) chitin synthetase of Mucor rouxii were investigated. The enzyme utilizes uridine diphosphate N-acetylD-glucosamine (UDP-GlcNAc) as glycosyl donor and is strongly and specifically activated by free N-acetyl-o-glucosamine (GlcNAc). A variety of GlcNAc analogues were tested as activators but were found ineffective. A small propo...

The administration of various polycyclic aromatic hydrocarbons to rats markedly increases the activity of several liver enzyme systems that metabolize certain drugs and other foreign compounds (14). The enzymes which respond to hydrocarbon administration belong to a group of microsomal enzymes that require reduced triphosphopyridine nucleotide for activity. Preliminary observations have suggest...

Long chain fatty acid:CoA ligase (EC 6.2.1.3.) was examined in human small intestinal mucosa using the hydroxamate-trapping method. With optimal assay requirements using palmitate as substrate a significant difference of specific activities could be detected in the total homogenate from duodenum, 40.9 +/- 11.6 nmol/min per mg protein versus upper jejunum, 51.9 +/- 13.7 (P less than 0.05). The e...

The accumulation of various 25-hydroxylated C(27)-bile alcohols in blood and their excretion in urine are characteristic features of cerebrotendinous xanthomatosis (CTX) a recessively inherited inborn error of bile acid synthesis caused by mutations in the mitochondrial sterol 27-hydroxylase (CYP27) gene. These bile alcohols may be intermediates in the alternative cholic acid side chain cleavag...

The Na/K-ATPase-rich microsomal fraction and purified Na/K-ATPase membranes of the salt-stressed avian salt gland were studied at defined filipin/cholesterol molar ratios (F/C) using enzyme assay and electron microscopy including negative staining, thin sectioning and freeze fracturing. Comparative examinations of detergent-treated microsomal fractions and the use of electron microscopic tracer...

Glucose 6-phosphatase from rat liver and kidney microsomes previously has been shown to catalyze an inorganic pyrophosphate-glucose phosphotransferase reaction. Nordlie and Soodsma recently have suggested that formation and then degradation of glucose 6-phosphate by the combined action of phosphotransferase and phosphohydrolase activities of this enzyme may under certain conditions constitute p...

The similarity in enzyme profile between microsomal preparations and nuclear envelopes has been shown for a range of enzymes in adult liver of various species (Franke, 1974; Kasper, 1974). The degree to which the enzymes in these two membrane systems can be induced is, however, variable. In rat liver, phenobarbital produced a two to three times increase in NADPH-cytochrome c reductase (EC 1.6.2...

The intracellular distribution of 5' nucleotidase was investigated in rat liver by biochemical analysis of cell fractions obtained by differential centrifugation. The enzymatic activity was measured by determination of the inorganic phosphorus liberated from 5' nucleotides. The 5' nucleotidase activity was mainly found in the nuclear and microsomal fractions. An attempt to extract the enzyme fr...

Sodium arsenite (NaAsO2), at 10% of its median lethal dose, was administered to rats with and without vitamin C pretreatment. Liver microsomal fraction was isolated and the activity of Ca2+-ATPase was assayed. Sodium arsenite was found to inhibit the activity of the liver microsomal Ca2+-ATPase to 50% to that of control rats. The specific activity of the enzyme in rats administered sodium arsen...

We have investigated the extent to which membrane environment affects the catalytic properties of the malonyl-CoA-sensitive carnitine acyltransferase of liver microsomal membranes. Arrhenius-type plots of activity were linear in the absence and presence of malonyl-CoA (2.5 microM). Sensitivity to malonyl-CoA increased with decreasing assay temperature. Partly purified enzyme displayed an increa...