Seibert V, Kourbatova E M, Golovleva L A, Schlömann M
Institut für Mikrobiologie, Universität Stuttgart, D-70569 Stuttgart, Germany.
J Bacteriol. 1998 Jul;180(14):3503-8. doi: 10.1128/JB.180.14.3503-3508.1998.
Maleylacetate reductases (EC 1.3.1.32) have been shown to contribute not only to the bacterial catabolism of some usual aromatic compounds like quinol or resorcinol but also to the degradation of aromatic compounds carrying unusual substituents, such as halogen atoms or nitro groups. Genes coding for maleylacetate reductases so far have been analyzed mainly in chloroaromatic compound-utilizing proteobacteria, in which they were found to belong to specialized gene clusters for the turnover of chlorocatechols or 5-chlorohydroxyquinol. We have now cloned the gene macA, which codes for one of apparently (at least) two maleylacetate reductases in the gram-positive, chlorophenol-degrading strain Rhodococcus opacus 1CP. Sequencing of macA showed the gene product to be relatively distantly related to its proteobacterial counterparts (ca. 42 to 44% identical positions). Nevertheless, like the known enzymes from proteobacteria, the cloned Rhodococcus maleylacetate reductase was able to convert 2-chloromaleylacetate, an intermediate in the degradation of dichloroaromatic compounds, relatively fast and with reductive dehalogenation to maleylacetate. Among the genes ca. 3 kb up- and downstream of macA, none was found to code for an intradiol dioxygenase, a cycloisomerase, or a dienelactone hydrolase. Instead, the only gene which is likely to be cotranscribed with macA encodes a protein of the short-chain dehydrogenase/reductase family. Thus, the R. opacus maleylacetate reductase gene macA clearly is not part of a specialized chlorocatechol gene cluster.
顺丁烯二酸乙酸还原酶（EC 1.3.1.32）已被证明不仅有助于细菌对一些常见芳香化合物（如喹啉或间苯二酚）的分解代谢，还能参与带有特殊取代基（如卤素原子或硝基）的芳香化合物的降解。到目前为止，编码顺丁烯二酸乙酸还原酶的基因主要在利用氯代芳香化合物的变形菌中进行了分析，在这些细菌中发现它们属于用于氯代儿茶酚或5-氯羟基喹啉周转的特殊基因簇。我们现已克隆了基因macA，它编码革兰氏阳性、降解氯酚的菌株红球菌1CP中（至少）两种顺丁烯二酸乙酸还原酶之一。macA的测序表明其基因产物与其变形菌对应物的亲缘关系相对较远（约42%至44%的相同位置）。然而，与已知的来自变形菌的酶一样，克隆的红球菌顺丁烯二酸乙酸还原酶能够相对快速地将二氯芳香化合物降解过程中的中间体2-氯顺丁烯二酸乙酸转化为顺丁烯二酸乙酸，并进行还原性脱卤。在macA上下游约3 kb的基因中，未发现有编码二醇双加氧酶、环异构酶或二烯内酯水解酶的基因。相反，唯一可能与macA共转录的基因编码一种短链脱氢酶/还原酶家族的蛋白质。因此，红球菌顺丁烯二酸乙酸还原酶基因macA显然不是特殊氯代儿茶酚基因簇的一部分。
