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Biosynthesis of methanopterin
1Department of Biochemistry and Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061-0308, USA.
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.
Insights
This study details the biosynthesis pathway of methanopterin in Methanosarcina thermophila, identifying key intermediates and reactions. The findings confirm the metabolic route through synthesis, detection, and conversion of these compounds.
Area of Science:
- Biochemistry
- Microbiology
- Metabolic Pathways
Background:
- Methanopterin is a crucial cofactor in methanogenic archaea.
- Understanding its biosynthesis is vital for comprehending methanogenesis.
Purpose of the Study:
- To elucidate the complete biosynthetic pathway of methanopterin in Methanosarcina thermophila.
- To identify and characterize the intermediate compounds involved in this pathway.
Main Methods:
- Chemical and biochemical synthesis of proposed pathway intermediates.
- Detection of intermediates in cell-free extracts of M. thermophila.
- Enzymatic assays to measure the conversion of intermediates.
Main Results:
- Established a step-by-step reaction sequence for methanopterin biosynthesis.
- Synthesized and identified key intermediates, including 7,8-H2pterin-6-ylmethyl-1-(4-aminophenyl)-1-deoxy-D-ribitol 5'-phosphate.
- Demonstrated the conversion of intermediates to demethylated H2methanopterin, a methanopterin precursor.
Conclusions:
- The proposed pathway for methanopterin biosynthesis in M. thermophila is validated.
- The study provides a comprehensive map of methanopterin production in this organism.