Abstract
1.
1. The ultrastructure of the flight muscle of the adult male grasshopper,
Poekilocerus bufonius, showed a variation in the shape and size of each individual myofibril profile which was in almost parallel register.
2.
2. Moderate number of mitochondria are present as well as high numbers of compact cristae.
3.
3. 6-Phosphofructo-1-kinase (PFK) from the flight muscle of
P. bufonius was purified more than 1000-fold to homogeneity with a yield of 77%.
4.
4. The sodium dodecyl sulphate-treated purified enzyme migrated as a single band in 7.5% polyacrylamide gel.
5.
5. The enzyme is a tetramer, with a monomer
M
r
82,000 ± 2000.
6.
6. The regulatory properties of the purified enzyme were studied at pH 7.0 and the affinity of the enzyme for fructose 6-phosphate was slightly increased by fructose 2,6-bisphosphate whereas the enzyme inhibition by high concentrations of ATP was slightly relieved by fructose 2,6-bisphosphate.
7.
7. The activity of flight muscle PFK was markedly inhibited by glucose 1,6-bisphosphate and phosphoarginine, and was weakly activated by ADP, AMP and fructose 2,6-bisphosphate.
8.
8. These data indicate that flight muscle PFK is not strongly affected by activators or by synergism between AMP and fructose 2,6-bisphopshate which is consistent with the fact that this insect is incapable of a long flight and the flight muscles of the adult females are very small and reduced to a thread-like structure.