. Author manuscript; available in PMC: 2009 Oct 27.

Published in final edited form as: J Am Soc Mass Spectrom. 2008 Jul 1;19(10):1459–1466. doi: 10.1016/j.jasms.2008.06.021

Table 1.

Comparison of kinetic constants of TPST-1, TPST-2, and 1:1 TPST-1 and -2 mixture

	Varied Substrate	K_m,app^a_μM	k_cat^b_min^-1	k_cat/K_m,app^c μM^-1 s^-1
Reaction 1: Monosulfation of nonCCR8
TPST-2	nonCCR8	1.2 × 10² ± 10	0.50 ± 0.03	0.075 ± 0.010
	PAPS	0.59 ± 0.10		14 ± 1
TPST-1	nonCCR8	99 ± 5	0.045 ± 0.007	0.0076 ± 0.0004
	PAPS	0.50 ± 0.09		1.5 ± 0.1
TPST-1 & -2, 1:1 mixture	nonCCR8	75 ± 4	0.43 ± 0.10	0.096 ± 0.005
	PAPS	0.54 ± 0.09		13 ± 1

Reaction 2: Disulfation of sY15CCR8
TPST-2	sY15CCR8	23 ± 2.6	0.30 ± 0.01	0.21 ± 0.02
TPST-1	sY15CCR8	21 ± 0.1	0.02 ± 0.00	0.014 ± 0.001
TPST-1 & -2, 1:1 mixture	sY15CCR8	17 ± 0.5	0.29 ± 0.01	0.29 ± 0.01

K_m,app is the apparent Michaelis constant at a particular substrate at saturating co-substrate concentration;

k_cat is the parameter that measures how fast the enzyme can turnover a substrate to product given [E]_total, k_cat = V_max/[E]_total;

K_cat/K_m,app measures how efficient an enzyme in catalyzing the reaction.

For Reaction 1, experiments when nonCCR8 and PAPS are varied were performed while keeping the cosubstrate (PAPS and nonCCR8, respectively) at constant and saturating concentrations. For Reaction 2, sY15CCR8 concentrations were varied while keeping PAPS constant at 1 mM. The experimental details and data analyses are as described under “Experimentals”. All experiments were performed 3 trials each (n=3).