AllD plays a pivotal role as a metabolic branch-point enzyme in nitrogen utilization via the assimilation of allantoin. It is able to utilize allantoin as a sole source of nitrogen under anaerobic conditions. Catalyzes the oxidation of ureidoglycolate to oxalurate. (S)-ureidoglycolate + NAD(+) = H(+) + N-carbamoyl-2-oxoglycine + NADH Nitrogen metabolism; (S)-allantoin degradation; oxalurate from (S)-ureidoglycolate: step 1/1. Homodimer. By glyoxylate and allantoin under anaerobic conditions. Belongs to the LDH2/MDH2 oxidoreductase family.