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Modifications induced by acylphosphatase in the functional properties of heart sarcolemma Na + ,K + pump
Author(s) -
Nassi Paolo,
Nediani Chiara,
Fiorillo Claudia,
Marchetti Elena,
Liguri Gianfranco,
Ramponi Giampietro
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80639-x
Subject(s) - sarcolemma , chemistry , atp hydrolysis , substrate (aquarium) , atpase , biochemistry , vesicle , hydrolysis , enzyme , biophysics , membrane , biology , ecology
Acylphosphatase purified from cardiac muscle actively hydrolyzes the phosphoenzyme intermediate of heart sarcolemma Na + ,K + ‐ATPase. This effect occurred with acylphosphatase amounts (up to 800 membrane protein) that fall within the physiological range and the low value of the apparent K m (0.69 × 10 −7 M) indicates a considerable affinity of the enzyme towards this specific substrate. Acylphosphatase addition to purified sarcolemmal vesicles significantly increased the rate of Na + ,K + ‐dependent ATP hydrolysis. Maximal stimulation, observed with 800 protein, resulted in an ATPase activity which was about 2‐fold over basal value. The same acylphosphatase amounts significantly stimulated, in a similar and to an even greater extent, the rate of ATP driven Na + transport into sarcolemmal vesicles. These findings lead to suppose that an accelerated hydrolysis of the phosphoenzyme may result in an enhanced activity of heart sarcolemmal Na + ,K + pump, therefore suggesting a potential role of acylphosphatase in the control of this active transport system.