Characterization of two pterin derivatives isolated from Methanoculleus thermophilicum.

Methanoculleus thermophilicum was shown to contain two pterin derivatives. The structures of these pterin derivatives were established from amino acid analysis, 1H-NMR and fast-atom bombardment mass spectrometry data. One of the pterins was identified as tatiopterin-O, an aspartyl derivative of methanopterin with a proton at position 7 of the pterin moiety. The other pterin, which we named thermopterin, differed in the structure of the aniline group, containing two additional hydroxyl residues. The IUPAC name of thermopterin is N-[-1'-(2"-amino-4"-hydroxy-6"-pteridinyl)ethyl]-4- [2',3',4',5'-tetrahydroxypent-1'-yl(5'----1") O-alpha-ribofuranosyl-5"-phosphoric acid]-2,5-dihydroxyaniline, in which the phosphate group is esterified with alpha-hydroxyglutarylaspartic acid.