Biosynthesis of Methanopterin in Methanobacterium thermoautotrophicum

Abstract

SummaryThe early steps in the biosynthesis of methanopterin in Methanobacterium thennoautotrophicum were analyzed by in vivo incorporation experiments of DC labeled precursors and by enzymatic studies. M thennoautotrophicum was grown in mineral medium supplemented with l3C-Iabeled acetate, pyruvate, or methionine. Methanopterin was isolated from the cells, and the I3.C-Iabeling pattern was determined by IH-and 13C_ NMR spectroscopy. The labeling patterns of amino acids and nucleosides were also determined for comparison. The results indicate that the pteridine moiety of methanopterin is derived from a purine nucleoside. Both methyl groups of methanopterin originate from methionine. The benzenoid ring of the ribitylaniline moiety is derived from the shikimate pathway, and the ribityl part from the pentose pool. Enrymatic activity of GTP cyclohydrolase I has been detected in cell-free supernatant of M thennoautotrophicum. This indicates that the early biosynthetic steps of folic acid and methanopterin proceed via common intermediates. Both pathways start from GTP, and 6-hydroxymethyldihydropterin is the probable branching point. The ribitylaniline moiety of methanopterin is synthesized from a product of the shikimate biosynthetic pathway and a ribose d~rivative, most probably p-aminobenzoate and phosphoribosylpyrophosphate, by decarboxylation of the aminobenzoate.

Use of Transposon Tn 5367 Mutagenesis and a Nitroimidazopyran-Based Selection System To Demonstrate a Requirement for fbiA and fbiB in Coenzyme F 420 Biosynthesis by Mycobacterium bovis BCG

“…The primers that corresponded to the known transposon sequence, HOPS1 and HOPS2, were taken from Bardarov et al (5). The random primer Semi-rand 2-1 was independently developed, but Semi-rand 4 was the same as (13,22,38), and including the role of 2-phospholactate proposed by Graupner and White (17). primer 4 of Chun et al (7).…”

“…The pathway by which F 420 is made has been explored with labeling approaches in methanogens (13,22,38). Also, recent enzymatic work with methanogens has shown that 2-phospholactate serves as a precursor of the lactyl and phosphate groups of F 420 (17).…”

A dicarboxylate/4-hydroxybutyrate autotrophic carbon assimilation cycle in the hyperthermophilic Archaeum Ignicoccus hospitalis

“…4, amino acids were isolated by chromatographic procedures as described in ref. 30, and 1 H and 13 C NMR spectra were recorded as described in ref. 4.…”

Demonstration that fbiC Is Required by Mycobacterium bovis BCG for Coenzyme F 420 and FO Biosynthesis

“…The Archaea M. thermoautotrophicum and Halobacterium sp., the green alga Scenedesmus acutus, and the cyanobacterium Synechocystis sp. use F 420 in photolyase (16,17,26,38).In M. thermoautotrophicum, the pathway by which F 420 is made has been studied with labeling (15,23,45) and enzymatic approaches (19), which have allowed development of a hypothetical pathway, an overview of which is shown in Fig. 1B.…”