Energy metabolism, enzymatic flux capacities, and metabolic flux rates in flying honeybees

Honeybees rely primarily on the oxidation of hexose sugars to provide the energy required for flight. Measurement of VCO₂ (equal to VO₂, because VCO₂/VO₂ = 1.0 during carbohydrate oxidation) during flight allowed estimation of steady-state flux rates through pathways of flight muscle energy metabolism. Comparison of V(max) values for flight muscle hexokinase, phosphofructokinase, citrate synthase, and cytochrome c oxidase with rates of carbon and O₂ flux during flight reveal that these enzymes operate closer to V(max) in the flight muscles of flying honeybees than in other muscles previously studied. Possible mechanistic and evolutionary implications of these findings are discussed.