FIGURE 2.

Identification of FT as a potential candidate for 5-CHO-THF removal. A, distribution among representative prokaryotes of the FT gene, of other histidine degradation genes (hutHUI, hutG, forI, nfoD, CD), and of the genes involved in 5-CHO-THF formation (glyA) and removal (ygfA). The tree shows the standard branching order for each group and is adapted from (60), with the addition of archaea (61) for which chemical, biochemical, or genomic evidence supports the presence of folates (15, 16, 62, 63). Note the anticorrelated distributions of ygfA and FT. Organisms whose FTs were tested experimentally are highlighted in yellow. B, histidine degradation pathways. Folate-dependent reactions are highlighted in pale blue. C, reactions mediated by mammalian FT, i.e. formimino or formyl group transfer between glutamate and THF. Abbreviations: hutH, histidine ammonia-lyase; hutU, urocanate hydratase; hutI, imidazolone propionase; hutF, formiminoglutamate iminohydrolase; hutG, formiminoglutamase; nfoD, N-formylglutamate deformylase; forI, formiminoglutamate iminohydrolase.