Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Active glycine transport was demonstrated in microvillous (maternal-facing, BBM) and basal (fetal-facing, BCM) plasma membranes of the human term placental syncytiotrophoblast. The kinetic studies showed that the amino acid had a distinct overshoot at 1 min in BBM and 3 min in BCM vesicles while a steady state rate was achieved in approx 5 min in both the vesicles. Glycine transport is highly ion-specific and its dependency on Na+ can not be satisfied by replacing with other monovalent cation. Cl- is also implicated in the generation of the electrochemical gradient and replacement of Cl- with SO4(2-) anions failed to stimulate the transport process. The transport process was saturable with external glycine which exhibited rectangular hyperbolic kinetics typical of a mediated movement. The calculated kt and Jmax from the linear transformation of the data were 6.67 & 4 mM and 294 & 263 nmoles glycine. mg protein-1.min-1 in the BBM and BCM vesicles, respectively. The glycine transport was inhibited by a number of other amino acids which are known to be transported through the A and ASC systems. The glycine transport system may be dependent on multiple pathways such as the A, ASC or Gly which is a variant of pathway A. Glycine transport was inhibited by ouabain, a known Na+/K+ -ATPase inhibitor, in the BCM vesicles but not in the BBM system. Nicotine, insulin, sodium fluoride and sodium arsenate were inhibitors for both the vesicles.
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PMID:Transport of glycine in the brush border and basal cell membrane vesicles of the human term placenta. 893 15

We have analyzed the effect of ischemia-reperfusion on expression of hepatic Na+,K+-ATPase on bile canalicular (BCM) and basolateral membranes (BLM) in human liver allografts using confocal laser scanning microscopy imaging. Na+, K+-ATPase, an integral membrane enzyme, plays a key role in the physiology and structure of hepatocytes, where it maintains the electrochemical gradients for Na+ and K+ across the cell membrane. The concentrations of these ions as well as their gradients regulate the active transport across the plasma membrane for bile acid and water from sinusoidal to canalicular membranes. In addition, Na+,K+-ATPase is also involved in cellular structure because of its close relationship with submembrane microfilaments and its implication in tight junction assembly. Therefore, Na+,K+-ATPase appears as an indicator of tissue viability and hepatic functionality during liver transplantation. Its localization and its function in BCM are still controversial. As in previous studies, we found an enzyme expression in both BLM and BCM. We show that ischemia induced a decrease in Na+,K+-ATPase expression only in BCM. This result could be explained by the differences in biochemical membrane environment between basolateral and bile canalicular Na+,K+-ATPase. Membrane lipid fluidity, which is more elevated in BLM than in BCM, could protect the enzyme during ischemia. After reperfusion, Na+,K+-ATPase expression was strongly decreased in both BCM and BLM. This alteration following reperfusion is probably due to multiple factors: direct alteration of the enzyme catalytic subunit and modification of its environment and membrane lipid fluidity by free radicals and changes in ATP levels and ionic distribution. This important decrease in Na+,K+-ATPase expression of both BLM and BCM could disturb not only hepatic secretory function but also cellular volume and structure during the postoperative period.
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PMID:Effect of ischemia-reperfusion on Na+, K+-ATPase expression in human liver tissue allograft: image analysis by confocal laser scanning microscopy. 1548 8