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. 2016 Jun 1;311(1):C150–C157. doi: 10.1152/ajpcell.00084.2016

Table 1.

Influx kinetics for pemetrexed and methotrexate for wt-PCFT and the W299S mutant

wt-PCFT W299S W299S/wt-PCFT
Pemetrexed Kt, μM 0.99 ± 0.23 0.28 ± 0.01 0.28
Pemetrexed Vmax, pmol/mg protein 384 ± 83 58.3 ± 8.7 0.15
Pemetrexed Ki, μM 0.94 ± 0.07 0.16 ± 0.02 0.17
MTX Ki, μM 2.36 ± 0.06 1.05 ± 0.03 0.44

Values are the mean ± SE from 3 independent experiments. Influx Kt, Ki and Vmax were computed from the Michaelis-Menton equation. All differences between wild-type proton-coupled folate transporter (PCFT) (wt-PCFT) and the W299S mutant are significant to P ≤ 0.01. The difference between the fold decrease in the influx Ki for the W299S mutant relative to wt-PCFT for both [3′,5′,7-3H]methotrexate (MTX) and pemetrexed is significant (P < 0.03). The difference between MTX Ki and pemetrexed Ki for wt-PCFT as well as the difference between the W299S mutants is significant (P < 0.003).