Sequence, expression, and characterization of the first archaeal ATP-dependent 6-phosphofructokinase, a non-allosteric enzyme related to the phosphofructokinase-B sugar kinase family, from the hyperthermophilic crenarchaeote Aeropyrum pernix

Abstract.

The gene (ORF APF0012) encoding the ATP-dependent 6-phosphofructokinase (ATP-PFK) of the hyperthermophilic archaeon Aeropyrum pernix was identified, cloned, and functionally expressed in Escherichia coli. The deduced amino acid sequence showed similarity (25–40%) to members of PFK-B sugar kinases. The purified recombinant enzyme is a heterotetramer of 115 kDa, composed of 34-kDa subunits. Rate dependence (at 85 °C) on both fructose 6-phosphate (F-6-P) and ATP followed Michaelis-Menten kinetics with apparent K _m values of 0.25 mM and 0.68 mM, respectively; apparent V _max values were about 5 U/mg. The enzyme was specific for ATP as phosphoryl donor, but showed a broader spectrum of phosphoryl acceptors: in addition to F-6-P, glucose 6-phosphate, adenosine, fructose, ribose 5-phosphate, and ribose were accepted. Enzyme activity required divalent cations; Mg²⁺, which was most effective, could partially be replaced by Co²⁺, Ni²⁺, or Mn²⁺. The enzyme had a temperature optimum of 90 °C and showed a significant thermostability up to 100 °C. ATP-PFK activity was not allosterically regulated by classical effectors of ATP-PFKs of eukarya and bacteria, such as ADP and phosphoenolpyruvate. In accordance, this archaeal ATP-PFK did not contain the typical conserved binding sites for these effectors. This is the first report of a sequence of an archaeal ATP-PFK related to the PFK-B sugar kinase family.