title: Phenotypes and circadian rhythm in utilization of formate in purine nucleotide biosynthesis de novo in adult humans.
abstract: OBJECTIVE
  Folate coenzymes and dependent enzymes introduce one carbon units at positions 2 (C(2)) and 8 (C(8)) of the purine ring during de novo biosynthesis. Formate is one source of one-carbon units. Although much is known about lower organisms, little data exists describing formate utilization for purine biosynthesis in humans.
  
  
  METHODS
  Mass-spectrometric analysis of urinary uric acid, the final purine catabolite, following 1.0 g oral doses of sodium [(13)C] formate was performed and detected (13)C enrichment at C(2) and C(8) separately.
  
  
  RESULTS
  Three phenotypes were suggested. One incorporates (13)C 0.72 to 2.0% into C(2) versus only 0 to 0.07% into C(8). Another incorporates only 0 to 0.05% (13)C into C(2) or C(8). A third phenotype incorporates (13)C into C(8) (0.15%) but C(2) incorporation (0.44%) is still greater. In subjects who incorporated (13)C formate into C(2), peak enrichment occurred in voids from 8-12 h (24 h clock) suggesting a circadian rhythm.
  
  
  CONCLUSIONS
  Evidence that mammalian liver introduces C(8) and that C(2) is introduced in a non-hepatic site would explain our results. Our data are not similar to those in non-mammalian organisms or cells in culture and are not consistent with the hypothesis that formate from folate-dependent metabolism in mitochondria is a major one carbon source for purine biosynthesis. Timing of peak (13)C enrichment at C(2) corresponds to maximal DNA synthesis in human bone marrow. Phenotypes may explain the efficacy (or lack of) of certain anticancer and immunosuppressive drugs.
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Baggott
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Gorman
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Morgan
mesh_terms: D000328:Adult; D002247:Carbon Isotopes; D002853:Chromatography, Liquid; D002940:Circadian Rhythm; D005650:Fumarates / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism; D010641:Phenotype; D011685:Purine Nucleotides / Q000096:biosynthesis*; D053719:Tandem Mass Spectrometry
chemical_list: D002247:Carbon Isotopes; D005650:Fumarates; D011685:Purine Nucleotides; C032005:fumaric acid