This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Häusler, R. E. Articles by Latzko, E. Search for Related Content PubMed PubMed Citation Articles by Häusler, R. E. Articles by Latzko, E. Agricola Articles by Häusler, R. E. Articles by Latzko, E.

Metabolism and Enzymology

Cytosolic ATP-Dependent Phosphofructokinase from Spinach

Botanisches Institut, Westfälische Wilhelms-Universität, Schloßgarten 3, 4400 Münster, Federal Republic of Germany

ATP-dependent 6-phosphofructokinase (PFK) activity is present in both chloroplastic and in nonchloroplastic fractions isolated from spinach protoplasts. The activity in the extra-chloroplastic fraction was stimulated 2- to 3.5-fold by 25 mM inorganic phosphate (Pi), the chloroplast-associated activity was inhibited 2- to 5-fold. The Pi stimulated activity was ATP-dependent and was not an artifact due to the presence of fructose 6-P, Pi, pyrophosphatase, and pyrophosphate fructose 6-P 1-phosphotransferase (PFP). PFK activities, which expressed characteristics similar to those separated from protoplasts, could be separated following ammonium sulfate fractionation of crude extracts; the ammonium sulfate treatment also separated both PFK activities from PFP. It is concluded that spinach leaves contain a cytosolic PFK. This activity is relatively stable, is stimulated by Pi over a wide pH range, is not a result of the transformation of another enzyme activity, and has an activity that is similar to, or slightly less than, that of the cytosolic PFP.