Members of this family appear to be found only in gamma proteobacteria. The function of this protein family is undetermined. Solution of the structures of the two members of this family investigated bear some resemblance to that of the single domain enzyme pterin-4a-carbinolamine dehydratase, PDC. Although the residues of PCDs involved in binding of metabolite are not conserved in the two structures under study, they do correspond to a surface-region structurally aligned with residues that are highly conserved, eg Glu 89, suggesting that this region is also involved in binding of a ligand, thereby possibly constituting a catalytic site of a yet uncharacterised enzyme specific for gamma proteobacteria.

1: Solution NMR structures of proteins VPA0419 from Vibrio parahaemolyticus and yiiS from Shigella flexneri provide structural coverage for protein domain family PFAM 04175. Singarapu KK, Mills JL, Xiao R, Acton T, Punta M, Fischer M, Honig B, Rost B, Montelione GT, Szyperski T; Proteins. 2010;78:779-784. PMID:19927321