Pig gastric microsomal (H+ + K+)-stimulated ATPase activity was nearly abolished within 10 min of digestion with phospholipase A2 at room temperature. The enzyme activity could be largely restored by a cytosolic activator protein partially purified from the gastric cells. The K+ sensitivity and turnover of 32P-labelled intermediates produced by the control and the activator-reconstituted micros...

Formation of 7 alpha-hydroxycholesterol by rat liver microsomes was quantitated using a gas chromatograph-mass spectrometer operated in selected ion monitoring mode. This procedure measures the mass of 7 alpha-hydroxycholesterol formed and does not require addition of labeled cholesterol to monitor the reaction, since endogenous microsomal cholesterol serves as substrate for the enzyme choleste...

Microsomal epoxide hydrolase plays a dual role in the activation and detoxification of carcinogenic compounds. Two polymorphic sites have been described in exons 3 and 4 of the microsomal epoxide hydrolase gene that change tyrosine residue 113 to histidine (Tyr113His) and histidine 139 to arginine (His139Arg), respectively. The exon 3 polymorphism reduces enzyme activity by approximately 50%, w...

Evidence is presented that a brain fraction containing synaptosomal membrane fragments and ghosts prepared from lysed rat forebrain synaptosomes synthesize protein in a cell free system. The protein synthesis was dependent upon the addition of a synaptosomal membrane fraction, Mg++, monovalent cations, ATP, GTP, and enzyme factors prepared from intact synaptosomes. Protein synthesis was inhibit...

Two widely used antipsychotic drugs, chlorpromazine (CPZ) and trifluoperazine (TFZ) inhibit NADPH-induced microsomal lipid peroxidation (LPO). Study of microsomal membrane fluidity revealed considerable disorganization in its architecture in the presence of NADPH, which can be restored back in the presence of CPZ and TFZ. NADPH-dependent microsomal LPO is catalyzed by NADPH: cytochrome P450 red...

Cytochrome P450s and glutathione-S-transferases (GSTs) constitute two of the largest groups of enzyme families that are responsible for detoxification of exogenous molecules in plants. Their activities differ from plant to plant with respect to metabolism and substrate specificity which is one of the reasons for herbicide selectivity. In the tuber forming yam bean, the legume Pachyrhizus erosus...

Microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase prepared from either rat liver or human fibroblasts was shown to be inactivated in vitro by a factor in extracts of cultured human fibroblasts in a reaction requiring ATP or ADP and Mg2+ or Mn2+. The inactivation factor was found in the soluble fraction of fibroblasts extracts and was shown to be heat-labile, nondialyzable, and precipit...

The effects of a new semisynthetic macrolide, roxithromycin, on drug metabolizing enzymes of rat liver were compared with two erythromycins, the base (EB) and the estolate (EE), after 7 days' treatment with high oral doses (400 and 800 mg/kg daily). Dose-related higher concentrations of roxithromycin were reached in serum and liver than after EB or EE. The two reference erythromycins induced th...

Evidence is presented that a brain fraction containing synaptosomal membrane fragments and ghosts prepared from lysed rat forebrain synaptosomes synthesize protein in a cell free system. The protein synthesis was dependent upon the addition of a synaptosomal membrane fraction, Mg++, monovalent cations, ATP, GTP, and enzyme factors prepared from intact synaptosomes. Protein synthesis was inhibit...

Levels of liver microsomal glucose 6-phosphatase (Reaction 1) are significantly stimulated in the diabetic or glucocorticoidtreated animal, and they are depressed after insulin administration or adrenalectomy (see, for example, References 1 to 8). This hydrolytic activity may play a physiologically significant role in the regulation of blood glucose and liver glycogen levels (1, 2, 9). Recent s...