Evolutionary distribution of deoxynucleoside 5-monophosphate N-glycosidase, DNPH1.

Deoxynucleoside 5-monophosphate N-glycosidase, DNPH1 is a member of the nucleoside 2-deoxyribosyltransferase (NDT) family. This enzyme catalyzes the hydrolysis of deoxynucleoside monophosphates into free nucleobase moieties and 2-deoxyribose 5-phosphates. The DNPH1 enzymatic activity was first demonstrated in rats and then in humans. Subsequently the DNPH1 gene was identified in a variety of organisms, mainly in Metazoa. Herein, we demonstrate that despite DNPH1 genes being distributed in almost all metazoans, the occurrence of DNPH1genes is mosaic. For example, they cannot be found anywhere in the entire clade of Sauropsida or anywhere in the whole phyla of Arthropoda and Ctenophora. Even among mammals, there are organisms without functional DNPH1 protein (Camelidae and most likely Cetacea). By our knowledge, the DNPH1 gene is missing in plants, fungi and in majority of protists. Accordingly, the enzyme is apparently not of vital importance in all the branches of the Tree of Life. Surprisingly the DNPH1 gene may be found in archaea as well as in bacteria. This refers to the origin of the gene from the period before the archaea branched off from other bacteria. We show that the genomic and protein primary structures of DNPH1 are highly conserved and any modification in such a structure would result in conversion to a pseudogene, which could possibly be eliminated from the genome.