TABLE 2

Kinetic constants for DAUN and DOX reduction by recombinant CBR1 wild-type and variant allele enzymes

Values correspond to mean ± S.D. obtained from three experiments performed with two independent enzyme preparations (n = 6) for each isoform.


Substrate

Kinetic Parameter

CBR1 Wild-Type

V88I Variant

P131S Variant
DAUN Vmax (nmol/min · mg of protein) 3430 ± 241 2090 ± 112* 3570 ± 176
Km (μM) 51 ± 13 51 ± 10 89 ± 5*
kcat (s-1)a 1.94 1.19 2.02
kcat/Km (s-1 M-1) 37.8 × 103 23.1 × 103 22.6 × 103
DOX Vmax (nmol/min · mg of protein) 364 ± 37 257 ± 11* 325 ± 40
Km (μM) 287 ± 57 335 ± 26 325 ± 72
kcat (s-1)a 0.21 0.15 0.18

kcat/Km (s-1 M-1)
7.2 × 102
4.4 × 102
5.7 × 102
  • * Significantly different from wild type (p < 0.05).

  • a kcat calculated from Mr 34,000.