Phosphorylation of the α and β polypeptides of the light-harvesting complex I (B870) of Rhodobacter capsulatus in an in vitro translation system

Abstract Sporozoites and unsporulated oocysts of Eimeria tenella were shown to contain a pyrophosphate-dependent phosphofructokinase (PP_i-PFK) but apparently lack an ATP-specific activity. The PP_i-PFK resembles those that occur in a number of other protists in being reversible and not subject to metabolic control. In contrast, the ADP-utilising pyruvate kinase, present in two developmental stages of the parasite, exhibited strong positive cooperativity with respect to its substrate, phosphoenolpyruvate, and was shown to be allostetically activated by glucose 6-phosphate, fructose 6-phosphate and AMP. It is suggested that the PP_i-PFK represents an adaptation of the parasite towards life in an environment containing only low concentrations of oxygen and that the unusual allosteric regulation of pyruvate kinase evolved to compensate for glycolysis not being controlled at the PP_i-PFK step.