Activity and properties of phosphofructokinase from while muscle of the horse mackerel Trachurus mediterraneus during simulation due to swimming

The activity and properties of phosphofructokinase (PFK) in tissues of horse mackerel which was swimming at burst regimen for 5 min and at cruiser one for 60 min have been investigated. In white muscle the PFK activity increased 1.6-fold after burst swimming and Hill's coefficient rose as well and decreased 3-fold after cruiser one. Swimming did not change the half-maximal saturation constant for both substrates and inhibition constants for ATP and citrate. In the preparations from white muscle of fish which were stimulated by burst swimming the PFK activity at physiological pH values (6.0-7.0) was higher comparing with one from the control group and after cruiser swimming. Incubation of preparations at 45 degrees C decreased the activity of PFK in control and cruiser swimming groups (to 61-67% of initial level) and increased it after burst swimming (1.3-fold). The mechanisms involving in stable modification of PFK under different swimming regimens are discussed.