Allosteric regulation of 6-phosphofructo-1-kinase activity of fat body and flight muscle from the bloodsucking bug Rhodnius prolixus

phosphofructo-1-kinase(phosphofructokinase;PFK)activityfromRhodniusprolixus,ahaematophagousinsectwhich is usually a poor flyer, was measured and compared in two metabolically active tissues - flight muscle and fat body. The activity of this important regulatory glycolytic enzyme was much more pronounced in muscle (15.1 ± 1.4 U/mg) than in fat body extracts (3.6 ±0.4 U/mg), although the latter presented higher levels of enzyme per protein content, as measuredbywestern-blotting. MuscleextractsaremoreresponsiblethanfatbodytoATPandfructose6-phosphate,both substrates of PFK. Allosteric regulation exerted by different effectors such as ADP, AMP and fructose 2,6-phosphate presented a singular pattern for each tissue. Optimal pH (8.0-8.5) and sensitivity to pH variation was very similar, and citrate was unable to inhibit PFK activity in both extracts. Our results suggest the existence of a particular PFK activity for each tissue, with regulatory patterns that are consistent with their physiological roles.