title: Biosynthesis of methanopterin.
abstract: This paper establishes the pathway for the biosynthesis of methanopterin in Methanosarcina thermophila to proceed by the following series of reactions. First, 5-phospho-alpha-D-ribosyl diphosphate (PRPP) and 4-aminobenzoic acid condense together to produce 4-(beta-D-ribofuranosyl)aminobenzene 5'-phosphate, which then reacts with 6-hydroxymethyl-7,8-H2pterin pyrophosphate to produce 7,8-H2pterin-6-ylmethyl-4-(beta-D-ribofuranosyl)aminobenz  ene 5'-phosphate (3'). Compound 3' is then reduced to 7,8-H2pterin-6-ylmethyl-l-(4-aminophenyl)-1-deoxy-D-ribitol 5'-phosphate (4') in a reaction stimulated by the addition of FMN or factor F(420). Dephosphorylation of compound 4' leads to 7,8-H2pterin-6-ylmethyl-1-(4-aminophenyl)-1-deoxy-D-ribitol (5'). Compound 5' then condenses with another molecule of PRPP to form 7,8-H2pterin-6-ylmethyl-1-(4-aminophenyl)-1-deoxy-5-[1-alpha -D- ribofuranosyl 5-phosphate]-D-ribitol (9'). Compound 9', in the presence of ATP, then condenses with (S)-2-hydroxyglutaric acid to form demethylated H2methanopterin, a known precursor to methanopterin. The occurrence of this pathway was confirmed by (a) the chemical and/or biochemical synthesis of most of the proposed intermediates, (b) the detection of these intermediates in cell-free extracts, and (c) by the measurement of their conversion to demethylated methanopterin and/or other intermediates in the pathway.
authors.affiliation: Department of Biochemistry and Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061-0308, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: White
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry; D002474:Cell-Free System; D005977:Glutarates / Q000378:metabolism; D017020:Methanosarcina / Q000378:metabolism*; D011622:Pterins / Q000378:metabolism*; D012266:Ribose / Q000737:chemistry
chemical_list: D005977:Glutarates; D011622:Pterins; C019417:alpha-hydroxyglutarate; D012266:Ribose; C036686:methanopterin; D010129:4-Aminobenzoic Acid