A novel diphospho-P,P'-diester from Methanobacterium thermoautotrophicum

Abstract

A phosphorus-containing metabolite that accounts for up to 80% of the total phosphate in perchloric acid extracts of Methanobacterium thermoautotrophicum ATCC 29183 was purified by chromatography on an anion exchange column. The proton-decoupled 31P NMR spectrum of the sodium salt in D2O exhibits an AB quartet with lines at -9.48, -9.78, -10.78, and -11.08 ppm upfield from 85% phosphoric acid. The phosphorus-phosphorus coupling constant is 18.5 Hz, a value characteristic of a pyrophosphate linkage. The structure of this compound has been tentatively established as cyclic-2,3-diphosphoglycerate (Kanodia, S., and Roberts, M. F. (1983) Proc. Natl. Acad. Sci. U.S.A., in press). Although rapidly degraded in neutral cell extracts, the diphosphodiester was stable for hours in cells whose metabolism had been arrested by depletion of H2 from the medium. If the cells were transferred to phosphate-free medium in the presence of H2 and CO2, the diester disappeared in about one cell generation. These findings point to a possible role as a phosphate storage compound, but the real function(s) of this unusual diphosphodiester must await a complete analysis of its structure and further metabolic studies.