Abstract:The molybdenum cofactor (Moco) is composed of a pterin moiety, molybdate and an O- or S-substituent attached to the metal. The bacterial Moco contains a molybdopterin dinucleotide which consists of mo...The molybdenum cofactor (Moco) is composed of a pterin moiety, molybdate and an O- or S-substituent attached to the metal. The bacterial Moco contains a molybdopterin dinucleotide which consists of molybdopterin (MPT) and a mononucleotide linked by a pyrophosphate bridge. Bacterial MPT dinucleotides identified so far are molybdopterin cytosine dinucleotide (MCD), molybdopterin adenine dinucleotide (MAD), molybdopterin guanine dinucleotide (MGD) and molybdopterin hypoxanthine dinucleotide (MHD). MPT has been resolved in bacterial xanthine dehydrogenases. Most molybdoenzymes studied exhibit a high specificity for the type of pterin utilized, even under conditions of coexpression of different molybdoenzymes. We have obtained the Hydrogenophaga pseudoflava CO dehydrogenase pterin in amounts sufficient for structural analysis and describe the first 1H- and 13C-NMR spectra of a carboxamidomethylated MPT dinucleotide. The data fully agree with the chemical structure of a di(carboxamidomethyl)molybdopterin cytosine dinucleotide [di(cam)MCD]. Compound U, an excretion product of H. pseudoflava, was isolated and its chemical structure has been resolved as 2-amino-7-(l,2-dihydroxyethyl)-6-(methylthio)thieno[3,2-g]pteridine-4(3H)-one (urothione) employing uv-vis spectroscopy, electron impact mass spectroscopy, 1H-NMR spectroscopy and HPLC. Evidence is presented, that urothione emerges from the degradation of the H. pseudoflava CO dehydrogenase Moco. The degradational pathway involves release of Moco from the enzyme, its dissociation into molybdate and MCD and conversion of MCD to urothione via MPT, phospho norurothione and norurothione.Read More
Publication Year: 1993
Publication Date: 1993-07-26
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 20
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