Fructose 6-phosphate phosphorylation in Bacteroides species

6-Phosphofructokinase (6-PFK) activities have been measured in cell extracts from a number of Bacteroides species. Two main types of 6-PFK were found: an ATP-linked 6-PFK and a PPi-linked 6-PFK. In most strains both of these activities were found, although in two strains only ATP-linked 6-PFK was present. The PPi-linked 6-PFK activity was always higher, when both activities were present, and showed Michaelis-Menten kinetics with respect to fructose 6-phosphate. In contrast, the ATP-linked 6-PFK activity usually gave sigmoid kinetics with respect to fructose 6-phosphate, although several strains were found to have activities with Michaelis-Menten kinetics. Conditions for measuring maximum activities of ATP-linked 6-PFK were not identical for different strains, and the activities were rather unstable in extracts. The possible consequences of the observation that most Bacteroides strains possess both an ATP-linked and a PPi-linked 6-PFK are discussed.