Subcellular compartmentation of fructose 2,6-bisphosphate in oat mesophyll cells.

Evacuolated mesophyll protoplasts from oat (Avena sativa L.) were fractionated by a membrane-filtration technique. This method of rapid quenching of metabolic reactions permitted estimation of the in-vivo pools of fructose 2,6-bisphosphate (Fru2,6bisP) in the cytosol, chloroplasts and mitochondria. Vacuolar Fru2,6bisP was calculated as the difference between control protoplasts and evacuolated ones. The results indicate that Fru2,6bisP is exclusively cytosol-located in oat mesophyll protoplasts. Assuming a cytosolic volume of about 2 pl per evacuolated protoplast, the cytosolic concentration there was 11 μM if protoplasts were in darkness. Illumination of either control or evacuolated protoplasts resulted in a significant decrease in the Fru2,6bisP content within 5 min.