Table I.

Effect of leaf temperature on the activities of PPDK, PEP carboxylase, and Rubisco

Leaf TemperaturePPDK1-aPEP CarboxylaseRubisco
Vmax1-bMalate sensitivity1-cInitial1-dTotal1-e
°C μmol m−2s−1 % Inhibition μmol m−2 s−1
2815.7 ± 1308 ± 1451 ± 332 ± 231 ± 1
4059 ± 1
42.563 ± 3
4513.4 ± 1295 ± 1066 ± 26 ± 129 ± 3

All assays were conducted at 30°C. Values represent the mean ±se of four replicates for PPDK and PEP carboxylase, and three replicates for Rubisco.

    • F1-a PPDK assayed under conditions to preserve the in vivo activation state.

    • F1-b Assayed under optimal conditions to indicate total potential activity.

    • F1-c Assayed using limiting substrate in the presence or absence of 0.5 mm l-malate; indicates the in vivo activation state.

    • F1-d Initial activity measured immediately after extraction; indicates in vivo activity.

    • F1-e Total activity measured after incubating in CO2 and Mg2+ to fully activate Rubisco.