Table III.

First-order Rate Parameters (Fit to the First-order Exponential Equation [S] = [S₀]e^−kt) and Initial Rate of Dephosphorylation for Each Tyrosine by HCPTP-A and HCPTP-B

	k (min−1)		t1/2 (min)		Initial rate (10% decrease in [S]) (pmol min−1 μg−1 HCPTP)
Tyrosine	A	B	A	B	A	B
pY575	0.02 ± 0.001	0.02 ± 0.001	34.3	45.4	0.8	0.4
ppY588Y594	0.09 ± 0.007	0.11 ± 0.01	7.4	6.8	2.2	1.5
pY588Y594a	0.04 ± 0.004	0.04 ± 0.002	16.2	18.3	0.4	0.2
Y588pY594	0.05 ± 0.002	0.06 ± 0.001	13.8	10.7	0.8	0.5
pY772	0.12 ± 0.02	0.04 ± 0.002	5.8	19.4	4.9	0.8
pY960	—	0.04 ± 0.002	—	18.3	—	0.1

^aFor pY588Y594 the rate was fit from 10–60 min as this substrate increases for the first 10 min of the reaction.