Table 2. Kinetic properties of purified phosphorylated AtPPC1 compared with dephosphorylated AtPPC1.

Dephospho-AtPPC1 was obtained following In vitro dephosphorylation of purified AtPPC1 with bovine PP2A as described in the Experimental section and the legend to Figure 5. K_a and IC₅₀ values were determined using subsaturating (0.25 mM) PEP. All values were determined at pH 7.3 and represent means±S.E.M. of n=4 separate determinations. All values are given in mM.

Parameter	Phospho-AtPPC1	Dephospho-AtPPC1
Km(PEP)	0.18±0.02	0.34±0.01
Ka(Glc-6-P)	0.028*±0.001	ND*†
IC50(L-Asp)	1.14±0.01	0.52±0.04
IC50(L-malate)+0 mM Glc-6-P	0.68±0.04	0.30±0.03
IC50(L-malate)+0.2 mM Glc-6-P	1.5±0.04	0.61±0.01
IC50(L-malate)+2 mM Glc-6-P	9.1±0.3	5.5±0.2

*Saturating Glc-6-P elicited 1.8- and 1.2-fold increases in the activity of phospho- and dephospho-AtPPC1 respectively.

†ND, not determined. Weak Glc-6-P activation prevented accurate determination of the K_a(Glc-6-P) value of dephospho-AtPPC1.