Tetrahydromethanopterin,a coenzyme involved in autotrophic acetyl coenzyme A synthesis from 2 CO2 in Methanobacterium

Methanobacterium thermoautotrophicum, a methane forming archaebacterium, grows autotrophically by synthesizing activated acetic acid from 2 CO₂. It is demonstrated in vitro that the methyl group of acetate is derived from methenyl tetrahydromethanopterin, which is known to be a one-carbon carrying coenzyme in CO₂ reduction to methane. The direct acetate precursors are suggested to be methyl tetrahydromethanopterin (“activated methanol”) and “activated carbon monoxide”.