Table II.

Substrate specificity of the partially purified PM Ca2+-ATPase activity

Assay ConditionsNucleoside Triphosphatase Activity
ATPITP
nmol min−1 mg−1 protein
−Ca2+ 0.270.25
+Ca2+ 0.70  (0.43)0.64  (0.39)
+Ca2+ + CaM3.26  (2.99)3.04  (2.79)

Assays were performed as described in “Materials and Methods,” in the presence of 1 mm ATP or ITP; values in parentheses represent the Ca2+-dependent activities.