The enzyme catalyses a step in the biosynthetic pathway of 2-aminoethylphosphonate, a component of the capsular polysaccharide complex of?Bacteroides fragilis. Requires thiamine diphosphate and Mg2+?as cofactors. The enzyme is activated by the divalent cations Mg2+, Ca2+?and Mn2+. Pyruvate and sulfopyruvate can also act as substrates, but more slowly.