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What does E2P stand for?

E2P stands for ADP-insensitive phosphoenzyme


This definition appears very rarely

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Samples in periodicals archive:

ADP stimulates hydrolysis of the "ADP-insensitive" phosphoenzyme in Na+, K+-ATPase and Ca2+-ATPase. A S Hobbs, R W Albers.
2001a. ADPinsensitive phosphoenzyme intermediate of sarcoplasmic reticulum Ca2+-ATPase has a compact conformation resistant to proteinase K, V8 protease and trypsin (0) by S Danko, T Daiho, Y Yamasaki, M Kamidochi, H Suzuki, C Toyoshima.
It catalyzes Ca2+ transport coupled with ATP hydrolysis [1] and [2]. During the catalytic cycle, the enzyme forms four major intermediates, E2 and E1 (non-phosphorylated states), and E1P and E2P, which are ADP-sensitive phosphoenzyme and ADP-insensitive phosphoenzyme.
1 mM) Mg2+ in the ab- sence of KCl. These results demonstrate that ADP can enhance the rate of EzP hydrolysis in the cases of the Na+,K+-ATPase and Ca2+-ATPase. As a consequence measurement of “ADP-sensitive EP” may overestimate E1P. re- of ADP-stim- The Ca2+-ATPase from sarcoplasmic reticulum and the Na+,K+-ATPase have been shown to be mechanistically sim- ilar enzymes (1-3). Both are phosphorylated in cation-de- pendent steps and sequentially form ADP-sensitive (E,P) and ADP-insensitive (E2P) phosphoenzyme.
Biol. Chem. , 243:1957), the phosphoenzyme formed at 0 °C under otherwise identical conditions was insensitive to the addition of K ions but was dephosphorylated rapidly by ADP. This suggested that-the conformational transition from ADP-sensitive, K-insensitive Na pump phosphoenzyme (E,-P) to K-sensitive, ADP-insensitive phosphoenzyme (E2P) is blocked at 0°C. Since the ATP:ADP exchange reaction is a partial reaction of the overall enzyme cycle dependent upon the steady state level of E,-P that is regulated by [Na], we examined the effects of temperature on the curve relating [Na] to ouabain-sensitive ATP:ADP exchange.