Table 3.

Kinetic parameters Vmax and KM of TNAP pyrophosphatase and pyrophosphatase assay: effect of mercaptopyruvate (MPA) and cysteine combined. At least 4 sets of experiments in duplicates were performed. Values are mean ± standard deviation.

MPA, μM
Cysteine, μM
Phosphatase [Ca++] = [Mg++] = 1 mMPyrophosphatase [Ca++] = [Mg++] = 1 mM
VmaxKMVmaxKM
027 ± 1.727 ± 1.648 ± 1.489 ± 17
407.5 ± 1.8*5.7 ± 1.9*18 ± 5.1*71 ± 18
4003.3 ± 0.9*5.2 ± 0.7*16 ± 6.9*139 ± 118
40002.6 ± 0.4*15 ± 2.9*11 ± 3.7*85 ± 88
  • * Calculated value with MPA present is statistically significantly different (p < 0.05) from the value with no MPA.