Abstract

Lactococcus lactis 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 Lactobacillus gasseri 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 ¹⁴C-AMP in the presence of APCP, as well as incorporating ³²P-AMP. Furthermore, radioactivity was detected in the RNA/DNA of bacterial cells cultured in the presence of ³²P-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.

摘要

据报道，乳酸乳球菌不能直接掺入单核苷酸，而是需要在掺入之前通过核苷酸酶将其外部去磷酸化为相应的核苷。尽管已发现乳酸菌 Lactobacillus gasseri PA-3 (PA-3) 掺入了嘌呤单核苷酸，例如腺苷 5'-一磷酸 (AMP)，但尚不清楚这些细菌是直接掺入这些单核苷酸还是掺入它们去磷酸化成相应的核苷后。本研究评估了 PA-3 在存在或不存在 5'-核苷酸酶抑制剂 α,β-亚甲基 ADP (APCP) 的情况下是否掺入了放射性标记的单核苷酸。PA-3 占¹⁴在 APCP 存在下的 C-AMP，以及结合³² P-AMP。^{此外，在32} P-AMP存在下培养的细菌细胞的 RNA/DNA 中检测到放射性。总之，这些发现表明 PA-3 直接掺入了嘌呤单核苷酸，而不是在它们去磷酸化为嘌呤核苷之后，并且 PA-3 在 RNA 和 DNA 的合成中利用了这些嘌呤单核苷酸。虽然需要更多的研究来鉴定 PA-3 中的嘌呤单核苷酸转运蛋白，但这项研究首次表明一些乳酸菌直接掺入嘌呤单核苷酸并将其用于生长。