TABLE 2.

Kinetic solvent isotope effects in PP_i hydrolysis by mPPases

Enzyme	Transport specificity	Assay conditions	V H, nmol·min−1·mg−1	ϕ
Tm‐mPPase	Na+	pHread 6.2, 50 mM K+, 10 mM Na+	320 ± 10	0.66 ± 0.02
Da‐mPPase	Na+	pHread 8.5, 100 mM K+, 10 mM Na+	360 ± 10	0.64 ± 0.01
Mm‐mPPase	Na+	pHread 7.2, 100 mM K+, 10 mM Na+	1,400 ± 20	0.66 ± 0.01
Bv‐mPPase	Na+ and H+	pHread 6.7, 50 mM K+, 10 mM Na+	108 ± 1	0.59 ± 0.03
Dh‐mPPase	H+	pHread 6.7, 50 mM K+	950 ± 10	0.67 ± 0.01