Table 3.

Apparent Km (Phosphate), Km (Glc6P), and Ki Values of the Recombinant GPT from Pea Roots for Various Phosphorylated Metabolites

Kinetic Constants for the Transport of
Substrate32P-Phosphatea14C-Glc6Pa
Km (app) (mM)
1.1 ± 0.10.7 ± 0.1
K (app) (mM)
Phosphatenone0.6 ± 0.1
Glc6P1.1 ± 0.1none
TrioseP0.6 ± 0.10.4 ± 0.1
3-PGA1.8 ± 0.11.3 ± 0.1
PEP2.9 ± 0.2<7
  • a The transport activites of 32P-phosphate and 14C-Glc6P, respectively, were measured essentially as described in Methods and in footnote b of Table 2. All experiments were performed with lipo-somes that had been preloaded with 25 mM inorganic phosphate. Mean values are from three different experiments ±SE.