Brain Transferase Research Articles

P3-232 - Effects of bifemelane hydrochloride on muscarinic receptors and choline acetyl transferase in brain of partial cerebrovascular insufficient aged rats

P3-232 - Effects of bifemelane hydrochloride on muscarinic receptors and choline acetyl transferase in brain of partial cerebrovascular insufficient aged rats

Biosynthesis of phosphatidic acid in rat brain via acyl dihydroxyacetone phosphate.

Abstract— The enzymes for the biosynthesis of phosphatidic acid from acyl dihydroxyacetone phosphate were shown to be present in rat brain. These enzymes were mainly localized in the microsomal fraction of 12–14 day old rat brains. The brain microsomal acyl CoA: dihydroxyacetone phosphate acyl transferase (EC 2.3.1.42), exhibited a broad pH optimum between pH 5 and 9 with maximum activity at pH 5.4. Km for DHAP at pH 5.4 was 0.1 mm and Vmax was 0.86nmol/min/mg of microsomal protein. The corresponding microsomal enzyme for the glycerophosphate pathway (acyl CoA: sn‐glycerol‐3‐phosphate acyl transferase EC 2.3.1.15) was shown to have a different pH optimum (pH 7.6). On the basis of the differences in pH optima, differential effects of sodium cholate in the enzymes and a common substrate competition study, these acyl transferases were postulated to be two different microsomal enzymes.Acyl DHAP:NADPH oxidoreductase (EC 1.1.1.101) in brain microsomes was found to be quite specific for NADPH as cofactor, being able to utilize NADH only at very high concentrations. This enzyme exhibited a Km of 8.6 μm with NADPH and Vmx of 0.81 nmol/min/mg protein. The presence of these two enzymes and the known presence of l‐acyl‐sn‐glycerol‐3‐phosphate: acyl CoA acyl transferase in brain (Fleming & Hajra, 1977) demonstrated the biosynthesis of phosphatidic acid in brain via acyl dihydroxyacetone phosphate. Phosphatidic acid was shown to form when dihydroxyacetone phosphate, acyl CoA, NADPH and other cofactors were incubated together with brain microsomes. Further properties of the enzymes and the probable importance of the presence of this pathway in brain were discussed.

Biosynthesis of the Chondroitin Sulfate Proteoglycan: PURIFICATION AND PROPERTIES OF XYLOSYLTRANSFERASE

Abstract Xylosyltransferase from embryonic chick epiphyseal cartilage catalyzes the transfer of xylose from UDP-xylose to particulate endogenous acceptors or to an exogenous protein acceptor obtained by Smith degradation of bovine chondroitin sulfate-protein complex. Use of the exogenous protein acceptor enabled determination of enzymic activity independently of endogenous acceptors. Homogenization of cartilage in buffers containing from 0.2 to 1 m KCl followed by centrifugation at 105,000 x g yielded soluble fractions which contained from 65 to 95% of the xylosyltransferase activity. The remainder of the activity was associated with the 105,000 x g sediment. Soluble enzyme was fractionated with ammonium sulfate and purified by centrifugation on density gradients or by gel filtration resulting in a 50-fold purification. The specific activities of xylosyltransferase in embryonic chick cartilage, brain, liver, and intestine were compared; enzyme activity was highest in cartilage. The specific activity of the transferase in brain was 8% of that from cartilage, whereas liver and intestine exhibited no measurable activity with the exogenous acceptor. Xylosyltransferase catalyzes the first of the sequential glycosyltransferase reactions required for synthesis of the chondroitin sulfate-protein linkage region and formation of polysaccharide chains. It is postulated that xylosyltransferase controls the initiation of chondroitin sulfate chains on core protein. The level of xylosyltransferase in tissue appears to be correlated with amounts of the mucopolysaccharide synthesized.

Microdetermination of cathechol-o-methyl transferase in brain

Microdetermination of cathechol-o-methyl transferase in brain