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pubmed:abstractText |
Radioactively labeled carbon monoxide (CO) dehydrogenase has been obtained in good yield and purity from Pseudomonas carboxydoflava grown in the presence of [32P]phosphate. One enzyme molecule contained an average of 8.32 molecules of phosphate. The entire phosphate content was confined to 2 molecules of FAD and 2 molecules of a pterin. These were noncovalently bound. Molybdoenzyme cofactors could be extracted into N-methyl formamide; pterins were isolated by thin-layer chromatography. CO dehydrogenase contained a novel pterin, different from molybdopterin, which was also resolved in other bacterial molybdoenzymes. Therefore, it was tentatively named bactopterin. The characteristic features of bactopterin were as follows. A relative molecular mass, Mr, of 730 which was much greater than that of molybdopterin (330) (Mr values refer to molybdenum-free forms of the cofactors; presumably, the latter were also devoid of the sulfhydryl groups contained in the native compounds). A content of 2 molecules of phosphate/molecule compared to only 1 phosphate in molybdopterin. Bactopterin was three times less susceptible to air oxidation than molybdopterin. Native bactopterin was cleaved by perchloric acid into two phosphorous-containing fragments with Mr of 330 and 420. The smaller one is believed to be very similar to molybdopterin, the larger one was not a pterin but probably contained an aromatic structure.
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