Sequence analysis of the arginase/agmatine ureohydrolase family, impor
tant enzymes in arginine/agmatine metabolism and the urea cycle, revea
ls the similarity of arginases to formiminoglutamate hydrolase (hutG)
in Klebsiella aerogenes and to a previously unidentified open reading
frame adjacent to the HMf locus of the archaebacterium Methanothermus
fervidus. The gene structure and distribution of these homologous prot
eins across primary kingdoms suggest that this family is another examp
le of a primordial enzyme possibly present in the universal common anc
estor and that can be used as phylogenetic marker.