TABLE 4.

Kinetic parameters of MKP5, HePTP, and PP2Cα (pH 7.0, 10 mm Mg2+, 25 °C)

Phosphatase	Substrate	kcat	Km	kcat/Km
		s–1	μm	m–1 s–1
MKP5	p38α/pTpY	0.55 ± 0.01	0.14 ± 0.01	(4.01 ± 0.42) × 106
	p38α/pT	0.42 ± 0.02	0.33 ± 0.04	(1.28 ± 0.21) × 106
	p38α/pY	0.78 ± 0.02	0.46 ± 0.032	(1.69 ± 0.16) × 106
	pNPP	0.22 ± 0.01	17680 ± 755	12.4 ± 0.8
HePTP	p38α/pTpY	0.86 ± 0.03	2.86 ± 0.27	(3.0 ± 0.4) × 105
	p38α/pY	0.27 ± 0.01	2.37 ± 0.33	(1.14 ± 0.22) × 105
	pNPP	3.52 ± 0.12	8675 ± 74	406 ± 17
PP2Cα	p38α/pTpY		≫12	(6.55 ± 0.17) × 104
	p38α/pT	2.75 ± 0.31	15.5 ± 2.4	(1.77 ± 0.47) × 105
	pNPP (Mn2+)	0.75 ± 0.02	585 ± 75	(1.28 ± 0.20) × 103