A close homolog, designated MocB (mannityl opine catabolism), is found in a mannopine catabolism region of a plasmid of Agrobacterium tumefaciens. However, it is not essential for mannopine catabolism, branches within the cluster of 6-phosphogluconate dehydratases (with a short branch length) in a tree rooted by the presence of other dehydyatases. It may represent an authentic 6-phosphogluconate dehydratase, redundant with the chromosomal copy shown to exist in plasmid-cured strains. This model includes mocB above the trusted cutoff, although the designation is somewhat tenuous. [Energy metabolism, Entner-Doudoroff]