Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.7 (acetylcholinesterase)
 28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microvessels were isolated from bovine and rat cerebral cortex by simple procedures involving mechanical homogenization, differential and density-gradient centrifugation, and chromatography on a column of glass beads. The preparations were composed of short capillaries with a diameter of 1-10 microns. Both purifications were monitored by assaying the activity of the marker enzyme gamma-glutamyl transpeptidase (gamma-GTase). The final bovine and rat preparations were enriched 20- and 14-fold over the homogenate respectively. gamma-GTase activity was measured in different fractions after bovine and rat membranes were solubilized with 0.5% and 0.3% Triton X-100 respectively. Measurement of 5'-nucleotidase and acetylcholinesterase activities indicated very low levels of contamination of the microvessel preparations by glial cells and neurons. The integrity of the capillary membranes was confirmed by the assay of a cytosolic marker enzyme, lactate dehydrogenase. Viability of the microvessels was demonstrated by the presence of detectable levels of adenylates and by tissue respiration induced by glucose and succinate. Comparison of the proteins of homogenized bovine and rat brain cortex with those of purified capillaries separated by SDS/PAGE revealed enrichment of at least three predominant proteins of 14, 16 and 18 kDa in the capillary preparations. It is concluded that these methods allow rapid isolation of small blood vessels of the blood-brain barrier which are suitable for metabolic and structural studies in vitro.
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PMID:Purification and characterization of metabolically active capillaries of the blood-brain barrier. 171 99

The transfer of detergent solubilized and purified gamma-glutamyl transpeptidase (gamma-GTase), of hog kidney cortex, from proteoliposomes into human erythrocyte ghost membranes has been studied. The transfer of gamma-glutamyl transpeptidase was observed upon incubation of gamma-GTase incorporated dipalmitoylphosphatidylcholine vesicles with erythrocyte ghost membranes at 37 degrees C for 12 h. The extent of transfer was dependent upon the fluidity of donor proteoliposomes, being more when dipalmitoylphosphatidylcholine proteoliposomes were used compared to dimyristoylphosphatidylcholine, and intermediate values were observed when binary mixtures of DMPC and DPPC were used. Moreover, the transfer of gamma-GTase was facilitated when rigid basic phospholipid proteoliposomes were used as donor. The transfer of gamma-GTase has been observed to be associated with the removal of intrinsic membrane proteins and lipids from erythrocytes, mainly acetylcholinesterase, sphingomyelin, and cholesterol. An enhancement in the fluorescence due to resonance energy transfer was observed when ghost membranes containing fluorescent donor probe were incubated with proteoliposomes containing fluorescent acceptor probe, indicating that fusion but not adsorption of vesicles occurs during the transfer process. However, the inability of entrapped [14C]-sucrose delivery from proteoliposomes into ghost membrane vesicle suggest that fusion per se is not primarily involved in the transfer process. It appears that the transfer of gamma-glutamyl transpeptidase occurs by a collisional transfer process resulting in intermembrane protein transfer. The gamma-glutamyl transpeptidase implanted ghost membranes exhibited the uptake of L-glutamate which was inhibited by serine-borate, an inhibitor of transpeptidase activity. In addition, the uptake of L-glutamate was inhibited by the dipeptide gamma-glutamyl-L-glutamate, thus supporting the proposed role of gamma-glutamyl transpeptidase in the uptake of amino acids in biological membranes.
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PMID:Proteoliposome interaction with human erythrocyte membranes. Functional implantation of gamma-glutamyl transpeptidase. 612 71