Characterization of Two Methanopterin Biosynthesis Mutants of Methylobacterium extorquens AM1 by Use of a Tetrahydromethanopterin Bioassay

摘要

An enzymatic assay was developed to measure tetrahydromethanopterin (H4MPT) levels in wild-type and mutant cells of Methylobacterium extorquens AM1. H4MPT was detectable in wild-type cells but not in strains with a mutation of either the orf4 or the dmrA gene, suggesting a role for these two genes in H4MPT biosynthesis. The protein encoded by orf4 catalyzed the reaction of ribofuranosylaminobenzene 5′-phosphate synthase, the first committed step of H4MPT biosynthesis. These results provide the first biochemical evidence for H4MPT biosynthesis genes in bacteria.