Isoform  Empirical Models^{a}, ^{b}, ^{c}  TwoSite Model  

K_{m} or S_{50}  V_{max}  n^{d}  K_{s}  V_{max}  α^{e}  
μM  pmol/min · mg protein  μM  pmol/min · mg protein  
1A1^{c}  345 ± 9  260 ± 6  1.3 ± 0.1  647 ± 18  249 ± 5  0.18 ± 0.02  
1A3^{b}, ^{f}  1768 ± 524  102 ± 24  1978 ± 190  87 ± 5  0.35 ± 0.12^{g}  
1A4  N.D.  
1A6^{c}  3.1 ± 0.02  19,596 ± 74  1.3 ± 0.01  6.7 ± 0.2  19,646 ± 127  0.22 ± 0.02  
1A7^{c}  1.4 ± 0.1  74 ± 2  2.3 ± 0.3  8.0 ± 0.9  77 ± 2  0.03 ± 0.01  
1A8^{c}  87 ± 6  1011 ± 37  1.5 ± 0.1  267 ± 84  1023 ± 37  0.11 ± 0.07  
1A9^{c}  1.3 ± 0.1  35 ± 0.8  2.2 ± 0.2  10 ± 1  37 ± 1  0.02 ± 0.004  
1A10^{a}  2.0 ± 0.1  1293 ± 26  
2B7^{c}  107 ± 5  44 ± 1  2.0 ± 0.2  668 ± 57  46 ± 1  0.03 ± 0.005  
2B15, 2B17  N.D. 





N.D., not determined.
↵ a MichaelisMenten, ^{b} Substrate inhibition, ^{c} Hill equation.
↵ d Hill equation coefficient.
↵ e Interaction factor from twosite model. β = 2, except for UGT1A3 since V_{max} is equivalent to 2K_{p}[E]_{t} for autoactivation (where [E]_{t} is the total enzyme concentration).
↵ f K_{si} = 938 ± 303 μM.
↵ g β = 0.11 ± 0.04.