Carbon dioxide fixation in trypanosomatids

Abstract

Fixation of carbon dioxide has been demonstrated for extracts fromCrithidia fasciculata, Trypanosoma megaandTrypanosoma brucei bruceibloodstream and culture forms. The enzymes involved in this fixation were found to be ADP-stimulated phosphoenolpyruvate carboxykinase (E.C. 4. 1. 1. 32), ‘malic’ enzyme (E.C. 1. 1. 138–40) and pyruvate carboxylase (E. 0. 6. 4. 1. 1). The subcellular localization of these enzymes has been investigated in all three organisms. Products of short and long term fixation experiments were separated and identified.The importance of carboxylation reactions is discussed in relation to the maintenance of oxidized and reduced coenzyme levels.