Alterations induced by acylphosphatase in the activity of heart sarcolemma calcium pump.
We studied the effect of muscle acylphosphatase on the Ca2+ pumping ATPase of heart sarcolemma. Acylphosphatase addition to calmodulin-depleted sarcolemmal vesicles produced a significant increase in the rate of Ca(2+)-dependent ATP hydrolysis, even higher than obtained with exogenously added calmodulin. Maximal stimulation (about four fold over basal value) was obtained with 550 units/mg vesicle protein, a concentration that fall within the physiological range. Conversely, similar amounts of acylphosphatase decreased the rate of ATP-dependent Ca2+ transport into the sarcolemmal vesicles. The maximal statistically significant inhibition of Ca2+ uptake was observed with the same acylphosphatase concentration that gave the maximal stimulation of Ca(2+)-ATPase activity. From these findings acylphosphatase appears to reduce the efficiency of heart sarcolemmal Ca2+ pump with an impairment of the coupling between ATP hydrolysis and Ca2+ transport. A possible mechanism of this effect is discussed.
Nediani
C
C
Dipartimento di Scienze Biochimiche, Università di Firenze, Italy.
Marchetti
E
E
Liguri
G
G
Nassi
P
P
D017766:Acid Anhydride Hydrolases; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D002417:Cattle; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism* / Q000494:pharmacology; D012508:Sarcolemma / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D000097024:Acylphosphatase
D017766:Acid Anhydride Hydrolases; D000255:Adenosine Triphosphate; D002118:Calcium; D000252:Calcium-Transporting ATPases; D010744:Phosphoric Monoester Hydrolases; D000254:Sodium-Potassium-Exchanging ATPase; D000097024:Acylphosphatase