EIMERIA-TENELLA CONTAINS A PYROPHOSPHATE-DEPENDENT PHOSPHOFRUCTOKINASE AND A PYRUVATE-KINASE WITH UNUSUAL ALLOSTERIC REGULATORS

Sporozoites and unsporulated oocysts of Eimeria tenella were shown to contain a pyrophosphate-dependent phosphofructokinase (PPi-PFK) but ap parently lack an ATP-specific activity. The PPi-PFK resembles those th at occur in a number of other protists in being reversible and not sub ject to metabolic control. In contrast, the ADP-utilising pyruvate kin ase, present in two developmental stages of the parasite, exhibited st rong positive cooperativity with respect to its substrate, phosphoenol pyruvate, and was shown to be allosterically activated by glucose 6-ph osphate, fructose 6-phosphate and AMP. It is suggested that the PPi-PF K represents an adaptation of the parasite towards life in an environm ent containing only low concentrations of oxygen and that the unusual allosteric regulation of pyruvate kinase evolved to compensate for gly colysis not being controlled at the PPi-PFK step.