TABLE 4

Transport kinetics of [3H]GlySar uptake in P. pastoris cells expressing different mammalian species of Pept1 gene

Parameter estimates are expressed as means ± S.E. (n = 9). The data were fitted to eq. 1 using a weighting factor of unity. GlySar concentrations ranged from 0.005 to 10 mM.

ParameterYeast Transformant
pPIC3.5KpPIC3.5K-hPept1pPIC3.5K-mPept1pPIC3.5K-rPept1
Vmax, pmol · OD−1 · min−1N.A.24.7 ± 2.461.5 ± 1.788.8 ± 1.5
Km, mMN.A.0.86 ± 0.250.30 ± 0.030.16 ± 0.01
Kd, μl · OD−1 · min−12.21 ± 0.142.21 ± 0.142.21 ± 0.142.21 ± 0.14
Vmax/Km, μl · OD−1 · min−1N.A.28.7205.0555.0
r20.8940.9330.9500.934
Gene copy numbera1.28 ± 0.011.05 ± 0.141.17 ± 0.230.97 ± 0.07
  • N.A., not applicable.

  • a Gene copy number was measured by real-time PCR using species-specific Pept1 gene primers and the ARG4 gene as a control; AOX1 gene primers were used for vector alone (Table 3).