Deoxynucleoside 5-monophosphate N-glycosidase or DNPH1 (former name Rcl) is a nucleotide hydrolase whose expression in mammalian cancer tissues has been associated with its tumorigenic potential. Therefore, the enzyme has been studied principally in rat and human models. We found the corresponding gene also in the freshwater sponge Ephydatia muelleri, an animal phylogenetically very distant from mammals. Here we report the expression and characterization of the recombinant DNPH1 from E. muelleri. The ancient homolog of mammalian enzyme in a sponge showed the substrate specificity and catalytic efficiency similar to that in higher animals. E. muelleri DNPH1 is inhibited by the purine nucleotides with different numbers of 5′-phosphate groups (n = 1–4). Our results demonstrate that GTP but also dGTP are the best inhibitors, followed by all other purine nucleotides that were tested. Hence, the functioning of DNPH1 in cells where the natural ATP and GTP concentrations are much higher than those of the substrates, dNMPs, should normally be downregulated. We demonstrate for the first time the existence of biologically relevant natural inhibitors of DNPH1, namely ATP and GTP.

脱氧核苷5一磷酸N-糖苷酶或DNPH1（以前的名称为Rcl）是一种核苷酸水解酶，其在哺乳动物癌症组织中的表达与其致癌潜能有关。因此，主要在大鼠和人类模型中研究了该酶。我们还在淡水海藻Ephydatia muelleri中发现了相应的基因，该动物在系统发育上与哺乳动物距离很远。在这里我们报告的表达和表征重组DNPH1从穆勒大肠杆菌。海绵中哺乳动物酶的古老同源物显示出与高等动物相似的底物特异性和催化效率。穆勒埃里希氏菌DNPH1被具有不同数量5'-磷酸基团的嘌呤核苷酸抑制（n = 1-4）。我们的结果表明，GTP和dGTP都是最好的抑制剂，其次是所有其他嘌呤核苷酸。因此，通常应下调自然ATP和GTP浓度远高于底物dNMP的细胞中DNPH1的功能。我们首次证明了DNPH1的生物学相关天然抑制剂的存在，即ATP和GTP。