TABLE 2.

Substrate spectrum of the recombinant AcmB_his^a

Substrate	Km (μM)	kcat (s−1)	kcat/km (s−1 M−1)
Cholest-4-en-3-one	42 ± 6	69 ± 4	1.6 × 106
Androst-4-en-3,17-dione	100 ± 12	82 ± 5	8.0 × 105
Progesterone	4 ± 1	43 ± 2	1.2 × 107
Testosterone	15 ± 3	33 ± 2	2.2 × 106
19-Nortestosterone	50 ± 9	26 ± 1	5.2 × 105
Cholest-5-en-3-one	9 ± 2	14 ± 0	1.6 × 106
Androsta-1,4-dien-3,17-dione		<1
5α-Cholestane		<1
Cholesterol		<1
Cholesta-3,5-diene		<1
Cortisone		<1
Corticosterone		<1
Estrone		<1

^aThe apparent K_m values and k_cat values (which refer to monomers of 62 kDa) were measured in triplicate at 37°C. The assay mixture contained 100 μM DCPIP, 2.8 μg enzyme, 100 mM Na⁺-phosphate (pH 6.0), and different concentrations of the respective substrate (1 to 500 μM).