<p>This family of bacterial proteins have been characterised as 4-deoxy-L-threo-5-hexosulose-uronate ketol-isomerase. It is coded for by kdul [<cite idref="PUB00014561"/>] and is involved in the fourth step in pectin degradation.</p><reaction> 4-deoxy-L-threo-5-hexosulose uronate = 3-deoxy-D-glycero-2,5-hexodiulosonate</reaction><p>Although this enzyme is found in <taxon tax_id="562">Escherichia coli</taxon>, its role is uncertain since E. coli is not known to degrade the polysaccharides which are potential sources of 5-keto-4-deoxyuronate [<cite idref="PUB00043775"/>].</p>