Metabolic Relationship Between the CO Dehydrogenase Molybdenum Cofactor and the Excretion of Urothione by Hydrogenophaga pseudoflava

Abstract

Urothione was isolated as an excretion product of Hydrogenophaga pseudoflava and other bacteria at amounts approaching 253 micrograms/l of culture corresponding to 44 micrograms/g bacterial dry mass. The compound was identified as urothione by co-chromatography with urothione isolated from human urine, its characteristic ultraviolet and visible absorption spectra, oxidation to pterin-6-carboxylic-7-sulfonic acid by alkaline permanganate, 1H-NMR spectroscopy, double-quantum-filtered Fourier-transform 1H correlated spectroscopy, circular-dichroism spectroscopy and mass spectroscopy. A metabolic relationship between urothione and the carbon monoxide dehydrogenase molybdenum cofactor was suggested by a 1.1:0.5 molar ratio between urothione excreted and degradation of carbon monoxide dehydrogenase, a coincidence of urothione excretion and induction of carbon monoxide dehydrogenase with different species of carboxidotrophic bacteria, a structural relationship between molybdopterin cytosine dinucleotide of the carbon monoxide dehydrogenase molybdenum cofactor and urothione, and the demonstrated conversion of the carbon monoxide dehydrogenase molybdenum cofactor to urothione in vitro. A pathway for the conversion of the H. pseudoflava carbon monoxide dehydrogenase molybdenum cofactor to urothione has been proposed which involves molybdopterin cytosine dinucleotide, molybdopterin, phospho-norurothione and norurothione.