. Author manuscript; available in PMC: 2016 Oct 15.

Published in final edited form as: Arch Biochem Biophys. 2015 Aug 28;584:61–69. doi: 10.1016/j.abb.2015.08.007

Table 2.

Steady state kinetics of substrate oxidation by CYP2B4 enzymes

Enzyme	7-EFC			7-BR
Enzyme	k_cat (min⁻¹)^a	K_M (μM)	k_cat/K_M	k_cat (min⁻¹) ^a	K_M (μmM)	k_cat/K_M
CYP2B4	7.4 ± 1.3	28.4 ± 7.6	0.26	1.96 ± 0.01	1.03 ± 0.22	1.90
F195W	12.9 ± 0.7	33.5 ± 14.1	0.39	1.83 ± 0.02	0.78 ± 0.07	2.35
F202W	0.3 ± 0.1	15.4 ± 8.8	0.02^b	N.D.
I241W	2.4 ± 0.7	189.1 ± 73.8	0.01	N.D.

CYP2B6	8.1 ± 0.2	6.2 ± 0.6	1.31
F202W	N.D.

CYMAL-5	8.5 ± 0.2	18.3 ± 2.4	0.46

Results are the average ± confidence interval calculated for p=0.05 of 3–4 independent experiments done in duplicate. N.D., not detectable above background; maximum fluorescence was less than twice the zero product value, corresponding to 7-HFC production rates <0.05 min−¹ or resorufin production rates <0.1 min⁻¹.

k_cat is a representation of nmoles of product produced per minute per nmole of CYP enzyme in the reaction.

Global fitting of data from three experiments was used due to the very low turnover of 7-EFC. Therefore the mean and standard deviation refer to the fit to the Michaelis-Menten equation not differences among experiments.