The Relevance of 5'-Nucleotidase Activity

My reason for looking into the 5'-nucleotidase issue is that I saw, in these two papers, that exogenous purines (http://jpet.aspetjournals.org/cgi/content/abstract/294/1/126 or http://www.ncbi.nlm.nih.gov/pubmed/10871303?dopt=Abstract) and pyrimidines (reference 28, cited in this: http://www.ncbi.nlm.nih.gov/pubmed/10354618) have both, separately, been shown or suggested to increase 5'-nucleotidase activity in those articles. It might be a factor limiting the dosages. But given that AICAR may be able to indirectly increase 5'-nucleotidase activity in methotrexate-treated cells, my thinking was that reduced folates could reduce 5'-nucleotidase activity by reducing AICAR accumulation. That effect could limit the indirect enhancement of 5'-nucleotidase activity by AICAR, thereby potentially buffering some of these apparently extreme enhancements of 5'-nucleotidase activity by exogenous nucleotides.