Promiscuity of methionine salvage pathway enzymes in Methanocaldococcus jannaschii

• DOI: 10.1099/mic.0.000670
• Publication Date: 2018-06-07T15:12:37Z
• Authors: Danielle V. Miller; Benjamin J. Rauch; Kim Harich; Huimin Xu; John J. Perona; Robert H. White
• Keywords: Nucleotide salvage

The methionine salvage pathway (MSP) is critical for regeneration of S-adenosyl-l-methionine (SAM), a widely used cofactor involved in many essential metabolic reactions. MSP has been completely elucidated aerobic organisms, and found to rely on molecular oxygen. Since anaerobic organisms do not use O2, an alternative pathway(s) must be operating. We sought evaluate whether the functions two annotated enzymes from Methanocaldococcus jannaschii, methylthioinosine phosphorylase (MTIP) methylthioribose 1-phosphate isomerase (MTRI), are consistent with functioning modified (AnMSP). show here that recombinant MTIP active six different purine nucleosides, its function as general nucleoside both AnMSP salvage. Recombinant MTRI 5-methylthioribose 5-deoxyribose substrates, which generated phosphororolysis 5'-methylthioinosine 5'-deoxyinosine by MTIP, respectively. Together, these data suggest may novel recycling 5'-deoxyadenosine moiety SAM M. jannaschii. These also enable biosynthesis 6-deoxy-5-ketofructose (DKFP), intermediate aromatic amino acid biosynthesis. Finally, we utilized homocysteine auxotrophic strain Methanosarcina acetivorans Δma1821-22Δoahs (HcyAux) identify potential intermediates vivo. Growth recovery experiments HcyAux were performed known proposed AnMSP. Only one metabolite, 2-keto-(4-methylthio)butyric acid, rescued growth absence homocysteine. This observation indicate pathways substantially differ among methanogens phylogenetically divergent genera.