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)

The sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) plays a critical role in Ca(2+) homeostasis via sequestration of this ion in the sarco/endoplasmic reticulum. The activity of this pump is inhibited by oxidants and impaired in aging tissues and cardiovascular disease. We have shown previously that the myeloperoxidase (MPO)-derived oxidants HOCl and HOSCN target thiols and mediate cellular dysfunction. As SERCA contains Cys residues critical to ATPase activity, we hypothesized that HOCl and HOSCN might inhibit SERCA activity, via thiol oxidation, and increase cytosolic Ca(2+) levels in human coronary artery endothelial cells (HCAEC). Exposure of sarcoplasmic reticulum vesicles to preformed or enzymatically generated HOCl and HOSCN resulted in a concentration-dependent decrease in ATPase activity; this was also inhibited by the SERCA inhibitor thapsigargin. Decomposed HOSCN and incomplete MPO enzyme systems did not decrease activity. Loss of ATPase activity occurred concurrent with oxidation of SERCA Cys residues and protein modification. Exposure of HCAEC, with or without external Ca(2+), to HOSCN or HOCl resulted in a time- and concentration-dependent increase in intracellular Ca(2+) under conditions that did not result in immediate loss of cell viability. Thapsigargin, but not inhibitors of plasma membrane or mitochondrial Ca(2+) pumps/channels, completely attenuated the increase in intracellular Ca(2+) consistent with a critical role for SERCA in maintaining endothelial cell Ca(2+) homeostasis. Angiotensin II pretreatment potentiated the effect of HOSCN at low concentrations. MPO-mediated modulation of intracellular Ca(2+) levels may exacerbate endothelial dysfunction, a key early event in atherosclerosis, and be more marked in smokers because of their higher SCN(-) levels.
 ...
PMID:Myeloperoxidase-derived oxidants inhibit sarco/endoplasmic reticulum Ca2+-ATPase activity and perturb Ca2+ homeostasis in human coronary artery endothelial cells. 2221 47

The enzymes involved in thiamine triphosphate (ThTP) metabolism in birds are not characterized so far. The aim of the present work was to study some properties of ThTPase in chicken liver. In liver homogenate, ThTPase activity has been found to display a bell-like pH-profile with a maximum of 5.5-6.0. Low activity was observed without divalent metal ions, while the addition of Mg2+ or Ca2+, each at 5 mM concentration, enhanced the rate of ThTP hydrolysis by a factor of 17-20. In the presence of 5 mM Mg2+ an apparent K(m) of the enzyme for ThTP was estimated by the method of non-linear regression as well as from the Hanes plot to be 1.7-2.2 mM. Monovalent anions such as I-, SCN-, NO3-, Br-, Cl- (at 150 mM concentration) showed inhibitory effect decreasing the rate of ThTPase reaction by 20-60%. After the homogenate was centrifuged, more than 85% of ThTPase activity was revealed in the fraction of insoluble particles indicating a membrane localization of the enzyme. The precipitate treatment with 1% sodium deoxycholate caused about 53% solubilization of the activity. During Toyopeal HW-55 chromatography, ThTPase activity was eluted simultaneously with ATPase and ITPase peaks in the void volume of the column. Thus, a non-specific high molecular mass protein complex seems to be involved in ThTP hydrolysis in the chicken liver. The chicken liver phosphatase is clearly distinguishable from all membrane-bound ThTPases reported previously.
 ...
PMID:[PROPERTIES OF CHICKEN LIVER MEMBRANE-ASSOCIATED THIAMINE TRIPHOSPHATASE]. 2650 98

We address advances in the understanding of myometrial physiology, focusing on excitation and the effects of gestation on ion channels and their relevance to labor. This review moves through pioneering studies to exciting new findings. We begin with the myometrium and its myocytes and describe how excitation might initiate and spread in this myogenic smooth muscle. We then review each of the ion channels in the myometrium: L- and T-type Ca2+ channels, KATP (Kir6) channels, voltage-dependent K channels (Kv4, Kv7, and Kv11), twin-pore domain K channels (TASK, TREK), inward rectifier Kir7.1, Ca2+-activated K+ channels with large (KCNMA1, Slo1), small (KCNN1-3), and intermediate (KCNN4) conductance, Na-activated K channels (Slo2), voltage-gated (SCN) Na+ and Na+ leak channels, nonselective (NALCN) channels, the Na K-ATPase, and hyperpolarization-activated cation channels. We finish by assessing how three key hormones- oxytocin, estrogen, and progesterone-modulate and integrate excitability throughout gestation. Expected final online publication date for the Annual Review of Physiology, Volume 83 is February 10, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
 ...
PMID:Uterine Excitability and Ion Channels and Their Changes with Gestation and Hormonal Environment. 3315 76


<< Previous 1 2 3 4 5 6 7 8 9 10