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First published online January 27, 2004
Journal of Experimental Biology 207, 749-754 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00825

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`Futile cycle' enzymes in the flight muscles of North American bumblebees

James F. Staples^*, Erin L. Koen and Terence M. Laverty

Department of Biology, University of Western Ontario, London, Ontario, Canada, N6A 5B7

View larger version (12K): [in a new window]   Fig. 1. The reactions catalyzed by phosphofructokinase (PFK) and fructose-1,6-bisphosphatase (FbPase). PFK phosphorylates fructose-6-phosphate (F6P), hydrolyzing ATP in the process. FbPase catalyses the hydrolysis of fructose-1,6-bisphosphate (F1,6bP) to F6P, releasing inorganic phosphate (Pi).

View larger version (23K): [in a new window]   Fig. 2. Activities of phosphofructokinase (PFK) and fructose-1,6-bisphosphatase (FbPase) in bumblebee thoracic flight muscle. Values are means ± S.E.M. Species with the same letters are not significantly different from each other (ANOVA). Sample sizes are as follows: B. terrestris, B. bimaculatus, B. impatiens, B. vagans, 10; B. perplexus, 5; B. rufocinctus, 6; B. griseocollis, 5; B. affinis, 2; Psithyrus citrinus, 3.

View larger version (17K): [in a new window]   Fig. 3. Ratio of phosphofructokinase (PFK) and fructose-1,6-bisphosphatase (FbPase) activities in flight muscle of individual bumblebees. Values are means ± S.E.M. Species with the same letters are not significantly different from each other (ANOVA). For sample sizes, see Fig. 2.

View larger version (11K): [in a new window]   Fig. 4. Allometric scaling of phosphofructokinase (PFK) activity in North American bumblebees. Abbreviations: b, B. bimaculatus; i, B. impatiens; v, B. vagans; r, B. rufocinctus; p, B. perplexus; g, B. griseocollis; c, Psithyrus citrinus; a, B. affinis; Mb, body mass.

View larger version (12K): [in a new window]   Fig. 5. Allometric scaling of fructose-1,6-bisphosphatase (FbPase) activity in North American bumblebees. For abbreviations, see Fig. 4.