Johnson J L, Rajagopalan K V, Meyer O
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
Arch Biochem Biophys. 1990 Dec;283(2):542-5. doi: 10.1016/0003-9861(90)90681-n.
The pterin cofactor (bactopterin) in the molybdoenzyme CO dehydrogenase isolated from Pseudomonas carboxydoflava has previously been shown to differ from molybdopterin in molecular mass, phosphate content, stability, and other properties, implying a novel structure. The structure of the CO dehydrogenase pterin has been investigated in the present studies by alkylation and isolation of the carboxamidomethyl derivative. The alkylated pterin was identified as [di-(carboxamidomethyl)]molybdopterin cytosine dinucleotide on the basis of its absorption properties and by degradation with nucleotide pyrophosphatase yielding carboxamidomethylmolybdopterin and CMP. Further treatment of these products with alkaline phosphatase produced species with absorption and chromatographic properties identical to those of the corresponding dephospho compounds. Molybdopterin cytosine dinucleotide is the second molybdopterin variant to be structurally characterized. The fact that molybdopterin cytosine dinucleotide and molybdopterin guanine dinucleotide contain molybdopterin in their structure shows that the pterin moiety, with its unique dithiolene-containing sidechain, is a structural element which is common to the organic portion of the molybdenum cofactors of many molybdoenzymes.
先前的研究表明，从食羧假单胞菌中分离出的钼酶一氧化碳脱氢酶中的蝶呤辅因子（细菌蝶呤）在分子量、磷酸盐含量、稳定性及其他性质方面与钼蝶呤不同，这意味着其结构新颖。在本研究中，通过对羧酰胺甲基衍生物进行烷基化和分离，对一氧化碳脱氢酶蝶呤的结构进行了研究。基于其吸收特性，并通过用核苷酸焦磷酸酶降解生成羧酰胺甲基钼蝶呤和CMP，将烷基化蝶呤鉴定为[二（羧酰胺甲基）]钼蝶呤胞嘧啶二核苷酸。用碱性磷酸酶对这些产物进行进一步处理，得到了具有与相应脱磷酸化合物相同吸收和色谱性质的物质。钼蝶呤胞嘧啶二核苷酸是第二种在结构上得到表征的钼蝶呤变体。钼蝶呤胞嘧啶二核苷酸和钼蝶呤鸟嘌呤二核苷酸在其结构中都含有钼蝶呤，这一事实表明，具有独特含二硫烯侧链的蝶呤部分是许多钼酶的钼辅因子有机部分共有的结构元件。
