Using EPUB, we conducted a preliminary biochemical characterization of AfG3PS, revealing it to be hyperthermophilic and ultrastable, even compared to related enzymes. AfG3PS is produced well in Escherichia coli (ca. 300 mg L -1 ), withstands pH values of 3-12 (Fig. ) and is deactivated slowly in nearly boiling water (mean lifetime ≈1 h at 95 °C, Fig. ). An Eyring plot of its deactivation rate estimates its half-life under ambient conditions at around 10 19 years (Fig. ). Although AfG3PS converts its native substrate 1 with a modest observed rate constant of only 2 min -1 at ambient temperature, its activity increases exponentially with temperature (Fig. ). Fitting with Macromolecular Rate Theory predicts its theoretical optimal temperature to lie well above 100 °C (Fig. ). AfG3PS is also extremely soluble and typically starts crystallizing spontaneously from dilute buffers when concentrated to >200 g L -1 .