Figure 5.
Dependence of AtPCOs 1–5 activity on O2 availability. Michaelis–Menten kinetic plots display the activities of AtPCOs 1–5 with respect to O2 concentration (using single time points within the linear rate range identified in Fig. S3). Assays were conducted at 25 °C using 50 mm Bis tris propane, 50 mm NaCl, and 5 mm TCEP, pH 8.0, as buffer. Peptide concentrations of 5 times the relative Km for AtRAP2(2–15) were used for analysis (given in the graph titles) to ensure that AtPCO turnover was not limited by peptide availability with the exception of AtPCO4, which was analyzed at 1 mm AtRAP2(2–15) to avoid the substrate inhibition region of this isoform (Fig. 4). Error bars display S.E. (n = 3).