. Author manuscript; available in PMC: 2009 Feb 20.

Published in final edited form as: J Biol Chem. 2006 May 30;281(35):25062–25075. doi: 10.1074/jbc.M600688200

Table 3. Kinetic parameters of T. vaginalis cysteine synthase.

	O-acetylserine sulphhydrylase			O-phosphoserine sulphhydrylase			Cysteine desulphurase
	K_m OAS (mM)	K_m Na₂S (mM)	k_cat (s⁻¹)	K_m OPS (mM)	K_m Na₂S (mM)	k_cat (s⁻¹)	K_m Cys (mM	K_m BME (mM)	k_cat (s⁻¹)
TvCS1	39.5 ± 2.9	0.8 ± 0.3	153 ± 44	227 ± 45	0.029 ± 0.002	165 ± 35	0.8 ± 0.3	3.4 ± 0.9	6.6 ± 1.2
ApCS¹	21	0.3	156	250	12.5	14000
StCS-B²	1.0 ± 0.6	0.006 ± 0.003	130 ± 17
StCS-B²	0.9 ± 0.1	0.01 ± 0.00	115 ± 12
AtCS³	1.4 ± 0.2	0.22 ± 0.09	1780 ± 280

Kinetic parameters of TvCS1 compared with other CSs. O-acetylserine sulphhydrylase activity: K_m O-acetylserine (OAS) and K_m sodium sulphide (Na₂S) were determined using 3 mM sodium sulphide and 100 mM O-acetylserine, respectively. K_cat shown is the mean calculated from values for V_max obtained from both the OAS and Na₂S saturation curves. O-phosphoserine sulphhydrylase activity: K_m O-phosphoserine (OPS) and K_m sodium sulphide (Na₂S) were determined using 2 mM sodium sulphide and 100 mM O-phosphoserine, respectively. K_cat was calculated from the O-phosphoserine saturation curves only, because it was not possible to use saturating amounts of O-phosphoserine (>500 mM) for the Na₂S saturation curves. Cysteine desulphurase activity: K_m cysteine (Cys) and K_m β-mercaptoethanol (BME) determined using 15 mM BME and 5 mM L-cysteine, respectively. Data were determined at 37°C and are means ± SD from 3 experiments.

Data from Mino and Ishikawa, 2003 (43). Kinetic parameters for O-acetylserine sulphhydrylase reaction determined at 60°C and for O-phosphoserine sulphhydrylase reaction determined at 85°C.

Data from Tai et al., 1993 (55). Kinetic parameters for O-acetylserine sulphhydrylase reaction determined at 25°C.

Data from Bonner et al., 2005 (30). Kinetic parameters for O-acetylserine sulphhydrylase reaction determined at 25°C.