<p>This bifunctional enzyme catalyses the condensation of formaldehyde with tetrahydromethanopterin (H4MPT) to 5,10-methylenetetrahydromethanopterin and the formation of ribulose-5-phosphate and formaldehyde from 3-hexulose-6-phosphate. Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation of methanol to CO2 and in formaldehyde detoxification. The genome of <taxon tax_id="2208">Methanosarcina barkeri</taxon> contains both the faeA gene as well as a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity and hexulose-6-phosphate synthase (Hps) activity [<cite idref="PUB00053140"/>].</p>