Triosephosphate isomerase (TIM) catalyzes the interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phosphate in a reaction that is essential for organism survival under gluconeogenic growth conditions. During a recent search for latent enzymatic activities capable of complementing the auxotrophy of a TIM-deficient bacterium we identified YghZ, a promiscuous reductase that catalyzes the stereospecific reduction of L-glyceraldehyde 3-phosphate to yield glycerol 3-phosphate. In so doing, YghZ provides a novel metabolic bypass of the triosephosphate isomerase reaction. YghZ is phylogenetically conserved across diverse life forms and the closest mammalian homologue is the β-subunit of voltage-gated potassium channels. In this report, we demonstrate that purified YghZ associates with a heme cofactor, which may regulate the reductase activity of this enzyme in vivo. The physiological implications of this discovery will be discussed.