Table 3. Enzyme activity.

Enzyme	A23187	Hydrolytic activity(µmol Pi / (mg·min))		Turnover rate(s-1)
		Total protein	SERCA only
Native SERCA	present	4.3±0.1	∼8.5	15.6
	absent	0.68±0.08	∼1.4	2.6
Native Na,K-ATPase	---	11.8±0.7	---	30
Recombinant SERCA (WT)	present	0.28±0.04	∼9	16.5
	absent	0.15±0.02	∼0.5	0.9

Hydrolytic activity values, with the corresponding turnover rates, determined for native SERCA, native Na,K-ATPase and recombinant SERCA (WT) at 37°C. In the case of SERCA, the presence or absence of 2 µM calcium ionophore (A23187) is specified, and the activity values are expressed with respect to the total protein or to SERCA only (see text).