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. 2002 Sep;130(1):256–264. doi: 10.1104/pp.004507

Table II.

Peptide substrate steady-state kinetic parameters with three peptide substrates

SOS2 Mutant Peptide Substrate Kcat Km Kcat/Km
s−1 μm m−1 s−1
SOS2T168D p1 1.89 211 ± 3.9 0.89 × 104
p2 2.30 119 ± 2.8 1.93 × 104
p3 2.76 99 ± 1.1 2.79 × 104
SOS2T168DΔF p1 2.01 201 ± 3.1 1.00 × 104
p2 2.26 111 ± 1.8 2.04 × 104
p3 2.62 95 ± 1.5 2.76 × 104
SOS2T168DΔ308 p1 1.90 198 ± 5.1 0.96 × 104
p2 2.32 145 ± 4.1 1.60 × 104
p3 2.51 113 ± 4.8 2.22 × 104

Phosphorylation of the peptide substrate p1, p2, or p3 by SOS2T168D, SOS2T168DΔF, or SOS2T168DΔ308 was measured at optimal concentration of Mn2+ (2.5 mm). The kinetic parameters were determined by varying [p1], [p2], and [p3] while holding ATP at 10 μm. Kcat/Km is presented here as a measure of overall enzyme efficiency for each peptide substrate. Values are the means ± sd from three separate experiments.