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. Author manuscript; available in PMC: 2020 Jun 17.
Published in final edited form as: Chem Res Toxicol. 2019 Apr 10;32(6):1151–1164. doi: 10.1021/acs.chemrestox.9b00006

Table 2.

Michaelis–Menten Kinetic Constants for Terbinafine N-Dealkylation Pathways by CYP3A4a

steady-state kinetic constants for individual metabolitesc
pathway step substrate Vmax b Km (μM) V/K
pathway 1 1.1 terbinafine N-methyl-1-naphthyl-methylamine
1000 ± 65 150 ± 25 6.7
1.2 N-methyl-1-naphthyl methylamine 1-napthaldehyde
390 ± 28 110 ± 22 3.5
pathway 2 2.1 terbinafine desmethyl-terbinafine
1300 ± 63 86 ± 13 15
2.2a desmethyl-terbinafine 1-naphthyl-methylamine
570 ± 44 410 ± 54 1.4
2.2b desmethyl-terbinafine 1-naphthaldehyde
5900 ± 430 520 ± 63 11
pathway 3d,e 3.1 terbinafine 1-naphthaldehyde
5700 ± 190 110 ± 11 52
a

Data fit best to the Michaelis–Menten equation over the Hill equation (P < 0.05) shown in Figures 3, 4, and 5. Values shown with standard deviations.

b

Units are pmol/min/nmol of protein.

c

Quantitation of TBF-A catalytic efficiency was not possible due to variable Vmax values, while the Km values were consistent.

d

Pathway Step 3.2 was not studied due to the absence of authentic standards and low efficiency of the previous step in a human liver microsomal enzymatic system that obviates the significance of this pathway for TBF-A.

e

Limit of quantitation was calculated as the standard deviation of response divided by the slope of the standard curve.