6-Phosphofructo-1-kinase from the lipid-accumulating, non-fermentative, red yeast Rhodotorula glutinis

Abstract

6-Phosphofructo-1-kinase (PFK, EC 2.7.1.11) activity was detected in extracts of Rhodotorula glutinis grown on different nitrogen and carbon sources. The activity of PFK varied depending on the composition of the culture medium and on the state of growth. Using a carbon-limited medium containing glucose and a mixed organic/inorganic nitrogen source, maximal yield, activity and stability of PFK were found under aerobic conditions at the end of the exponential growth phase. Native Rhodotorula-PFK could be separated by polyacrylamide gel electrophoresis. Applying this method for molecular mass estimation a value of 450 ± 90 kDa was calculated. Taking into account a molecular mass of 130 ± 5 kDa for the subunit, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis following immunoblotting, a tetrameric structure of the native PFK is likely. Polyclonal antibodies, raised against PFK from Saccharomyces cerevisiae, were able to cross-react with Rhodotorula-PFK. Therefore, there are similarities in the primary structure of both enzymes. Fructose 2,6-bisphosphate was identified as a significant activator of Rhodotorula-PFK leading to a 10-fold activation of the enzyme: maximal activation was achieved with 5 μM fructose 2,6-bisphosphate.