PA-3 directly incorporates purine mononucleotides and utilizes them for growth.

has been reported unable to directly incorporate mononucleotides but instead requires their external dephosphorylation by nucleotidases to the corresponding nucleosides prior to their incorporation. Although PA-3 (PA-3), a strain of lactic acid bacteria, has been found to incorporate purine mononucleotides such as adenosine 5'-monophosphate (AMP), it remains unclear whether these bacteria directly incorporate these mononucleotides or incorporate them after dephosphorylation to the corresponding nucleosides. This study evaluated whether PA-3 incorporated radioactively-labeled mononucleotides in the presence or absence of the 5'-nucleotidase inhibitor α,β-methylene ADP (APCP). PA-3 took up C-AMP in the presence of APCP, as well as incorporating P-AMP. Furthermore, radioactivity was detected in the RNA/DNA of bacterial cells cultured in the presence of P-AMP. Taken together, these findings indicated that PA-3 incorporated purine mononucleotides directly rather than after their dephosphorylation to purine nucleosides and that PA-3 utilizes these purine mononucleotides in the synthesis of RNA and DNA. Although additional studies are required to identify purine mononucleotide transporters in PA-3, this study is the first to show that some lactic acid bacteria directly incorporate purine mononucleotides and use them for growth.