Citrate synthase from the thermophilic archaebacteria Thermoplasma acidophilum and Sulfolobus acidocaldarius

Citrate synthase has been purified to homogeneity from the thermophilic archaebacteria Thermoplasma acidophilum and Sulfolobus acidocaldarius. From the relative molecular masses of the native proteins (85 and 83 kDa, respectively) and of their polypeptide chains (43 and 41 kDa, respectively) it is established that they are dimeric enzymes. The N‐terminal sequence of the Thermoplasma citrate synthase was determined to be P‐E‐T‐E‐E‐I‐S‐K‐G‐L‐E‐D‐V‐N‐I‐K. These properties are compared with those of citrate synthases from eubacteria and eukaryotes to extend the pattern of structural and functional diversity previously observed for this enzyme in non‐archaebacterial species.