Calcium ATPase

Protein kinase A (PKA) is a cyclic AMP-dependent protein kinase, a member of a family of protein kinases that are activated by binding of cAMP to their two regulatory subunits, which results in the release of two active catalytic subunits. Targets of PKA include L-type calcium channels (the relevant subunit and site of phosphorylation is still uncertain), phospholam-ban (the regulator of the sarcoplasmic calcium ATPase, SERCA) and key enzymes of glucose and lipid metabolism. 

Sarcoplasmic calcium ATPase this enzyme utilizes the energy gained from hydrolysis of ATP to pump calcium from the cytosol into the stores of the sarcoplasmic reticulum. Its activity is negatively regulated by the closely associated protein phospholamban, and this inhibition is relieved upon phosphorylation of phospholamban by protein kinase A (PKA). 

Thiols are also important protection against lipid peroxidation. Glutathione (7-Glu-Cys-Gly) is used by several glutathione-dependent enzymes such as free-radical reductase (converts vitamin E radical to vitamin E), glutathione peroxidase (reduces hydrogen peroxide and lipid hydroperoxides to water and to the lipid alcohol, respectively), and others. In addition, the thiol group of many proteins is essential for function. Oxidation of the thiol of calcium ATPases impairs function and leads to increased intracellular calcium. Thiol derivatives such as the ovothiols (l-methyl-4-mercaptohistidines) (Shapiro, 1991) have been explored as therapeutics. 

Brody s disease is an unusual disorder of the sarcoplasmic reticulum calcium ATPase 723... 

MAHMA NONOate spontaneously dissociates in a pH-dependent, first-order process with a half-life of 1 min at 37 °C. In vivo, examination in anesthetised rats showed, that MAHMA NONOate had both platelet inhibitory and vasodepressor effects [50]. Like other NONOates, MAHMA NONOate inhibited collagen-induced and ADP-induced rat platelet aggregation in a concentration-dependent manner [51]. ODQ, a soluble GS inhibitor, caused only small influence on the concentration-response curve to MAHMA NONOate, indicating that cGMP-independent mechanisms play a crucial role. A potential target of MAHMA NONOate induced inhibition was the sarco-endoplasmic reticulum calcium-ATPase of the platelet dense tubular system... 

Mehorta and coworkers (1989) observed that isolated fractions of brain and heart cells from rats orally administered 0.5-10 mg endrin/kg showed significant inhibition of Ca+2 pump activity and decreased levels of calmodulin, indicating disruption of membrane Ca+2 transport mechanisms exogenous addition of calmodulin restored Ca+2-ATPase activity. In vitro exposure of rat brain synaptosomes and heart sarcoplasmic reticuli decreased total and calmodulin-stimulated calcium ATPase activity with greater inhibition in brain preparations (Mehorta et al. 1989). However, endrin showed no inhibitory effects on the calmodulin-sensitive calcium ATPase activity when incubated with human erythrocyte membranes (Janik and Wolf 1992). In vitro exposure of rat brain synaptosomes to endrin had no effect on the activities of adenylate cyclase or 3, 5 -cyclic phosphodiesterase, two enzymes associated with synaptic cyclic AMP metabolism (Kodavanti et al. 1988). 

Desaiah D, Chetty CS, Prasada Rao KS. 1985. Chlordecone inhibition of calmodulin activated calcium ATPase in rat brain synaptosomes. J Toxicol Environ Health 16 189-195. 

Mishra SK, Koury M, Desaiah D. 1980. Inhibition of calcium ATPase activity in rat brain and muscle by chlordecone. Bull Environ Contam Toxicol 25 262-268. 

Calcium ATPase Sarcoplasmic reticulum Triton X-100/phospholipids/toluene Conformational studies [77]... 

In conclusion, alkaline phosphatase, pyrophosphatase, and a calcium ATPase appear to be the same enzyme. The enzyme has three separate functions (1) breaking down ATP, (2) hydrolysing inorganic pyrophosphate and possibly other phosphate esters, and (3) opening of C—0-P bonds. In this capacity it has a profound impact on transport and regulation of phosphates and calcium, and is involved in biomineralization processes171 173. ... 

Hovnanian, A., 2004, Darier s disease from dyskeratosis to endoplasmic reticulum calcium ATPase deficiency. Biochem Biophys Res Commun, 322 1237—44. 

MacLennan, D. H., Toyofuku, T., and Kimura, Y., 1997, Sites of regulatory interaction between calcium ATPases and phospholamban. Basic Res Cardiol, 92 Suppl 1 11-5. 

Tavadia, S., Authi, K. S., Hodgins, M. B., and Munro, C. S., 2004, Expression of the sarco/endoplasmic reticulum calcium ATPase type 2 and 3 isoforms in normal skin and Darier s disease. Br J Dermatol, 151 440-5. 

Abstract The plasma membrane calcium ATPase (PMCA) uses energy to pump calcium (Ca2+)... 

Krizaj, D., Demarco, S.J., Johnson, J., Strehler, E.E., Copenhagen, D.R., 2002, Cell-specific expression of plasma membrane calcium ATPase isoforms in retinal neurons. J Comp Neurol 451, 1-21. 

Lee, W.J., Roberts-Thomson, S.J., Monteith, G.R., 2005a, Plasma membrane calcium-ATPase 2 and 4 in human breast cancer cell lines. Biochem Biophys Res Commun 337, 779-783. 

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