A phylogenetic
analysis of 11 different UMPS amino acid
sequences revealed three clades: one containing the
mammalian sequences, one formed of plant sequences
(with branches for monocots and dicots) and a third consisting
of the slime mold and Drosophila sequences (Park
and Thornburg, 2000). The evolutionary implications of the
mosaic pyrimidine-biosynthetic pathway in eukaryotes
have been described by Nara et al. (2000). During evolution
of eukaryotes, plants and fungi in particular may have
secondarily acquired the characteristic enzymes of this
pathway.