Model for the growth slowing effect of overexpressing FBPase in C. reinhardtii.
Overexpression of FBPase slows C. reinhardtii growth under photoautotrophic and high
CO2 conditions. One possible explanation for this effect is based on the assumption that
FBPase is not a rate-limiting enzyme in the algal Calvin cycle, and that one or more
other enzymes acting downstream of FBPase are. Compared to the situation in the wild
type (top), overexpression of FBPase might decrease pools of G3P available for synthesis
of hexose sugars by converting fructose -1,6-bisphosphate (FBP) into fructose -6-
phosphate (F6P), which would accumulate to higher levels than normal (bottom), or be
converted to another Calvin cycle intermediate that builds up due to a downstream
bottleneck in the pathway. The end result of FBPase overexpression would be reduced
hexose production and slower growth