TABLE 1

Kinetic properties of recombinant human UMP/CMP kinase in phosphorylating dCMP or CMP under different ATP/Mg2+ combinations

All reactions were performed at 37°C, using methods described under Materials and Methods. Km values were derived from Lineweaver-Burk plots. Vmax was calculated using the Michaelis-Menton equation: v = Vmax [S]/Km + [S]. Relative efficiency = Vmax/Km × 100%, relative to dCMP phosphorylation at ATP/Mg 8/8 mM. Values are presented as mean ± S.D. from at least three independent experiments.

Phosphate Acceptor ATP/Mg Kinetic Parameters
KmVmax Relative Efficiency
mM μM μmol/min/mg of protein %
dCMP 0.1/2 404 ± 23 413 ± 19 492
0.5/2 526 ± 70 540 ± 100 495
2/2 906 ± 36 420 ± 30 223
8/8 1388 ± 4 288 ± 3 100
CMP 0.1/2 5 ± 2 513 ± 88 49,400
0.5/2 N.D. N.D. N.D.
2/2 15 ± 6 543 ± 42 17,400
8/8 29 ± 11 620 ± 200 10,300
  • N.D. not done.