. Author manuscript; available in PMC: 2010 Mar 25.

Published in final edited form as: Mol Cell Endocrinol. 2008 Oct 8;301(1-2):174–182. doi: 10.1016/j.mce.2008.09.029

Table 4.

Cofactor kinetics for the 3β-HSD and isomerase activities for purified human P195R-2, 3β-HSD1 and 3β-HSD2

	3β-HSD¹			Isomerase²
Purified Enzyme	K_m μM	k_cat min⁻¹	k_cat/K_m min⁻¹ uM⁻¹	K_m μM	k_cat min⁻¹	k_cat/K_m min⁻¹ uM⁻¹
P195R-2	56.4 ± 3.2	9.2 ± 0.3	0.25 ± 0.02	10.0 ± 0.2	89.5 ± 5.8	8.9 ± 0.7
3β-HSD1	34.1 ± 1.7	3.5 ± 0.2	0.10 ± 0.005	4.6 ± 0.2	45.0 ± 1.8	9.8 ± 0.4
3β-HSD2	86.3 ± 5.6	7.1 ± 0.6	0.08 ± 0.005	12.6 ± 0.9	99.1 ± 6.4	7.9 ± 0.5

Kinetic constants for the 3β-HSD cofactor were determined in incubations containing NAD⁺, dehydroepiandrosterone and purified enzyme in 0.02 M potassium phosphate, pH 7.4, as described in Experimental Procedures.

Kinetic constants for the isomerase cofactor were determined in incubations of NADH, 5-androstene-3,17-dione and purified enzyme in 0.02 M potassium phosphate buffer, pH 7.4, as described in Experimental Procedures. All values are the means of triplicate determinations ± standard deviations.