RoxB Is a Novel Type of Rubber Oxygenase That Combines Properties of Rubber Oxygenase RoxA and Latex Clearing Protein (Lcp)
RoxB Is a Novel Type of Rubber Oxygenase That Combines Properties of Rubber Oxygenase RoxA and Latex Clearing Protein (Lcp)
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DOI：
10.1128/aem.00721-17
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发表时间：
2017-07-01
影响因子：
4.4
通讯作者：
Jendrossek, Dieter
中科院分区：
文献类型：
--
作者：
Birke, Jakob;Roether, Wolf;Jendrossek, Dieter
橡胶加氧酶只有两种类型，橡胶加氧酶（RoxA）和胶乳清除蛋白（LCP），迄今已被描述。RoxA蛋白（RoxA）是由革兰氏阴性橡胶降解菌产生的分子量约为70 kDa的C型细胞色素，其主要终产物为12-氧代-4，8-二甲基十三碳-4，8-二烯-1-醛（12-oxo-4，8-dimethyltrideca-4，8-diene-1-al，ODTD）。Lcp在革兰氏阳性橡胶降解菌中很常见，并且与RoxA没有氨基酸序列相似性。此外，Lcp具有小得多的分子量（约40 kDa），是b型细胞色素，并将聚异戊二烯裂解成C-20、C-25、C-30和更高级的寡聚类异戊二烯的混合物作为终产物。本文从黄单胞菌35 Y菌株中分离纯化了一种新型橡胶加氧酶RoxB Xsp（RoxB）。RoxB Xsp与RoxA有远亲关系，在分子量（成熟蛋白为70.3 kDa）和辅因子含量（2个C型血红素）方面与RoxA相似。然而，RoxB Xsp与所有目前已知的RoxA的不同之处在于具有独特的C20、C25、C30和更高级的低聚类异戊二烯的产物谱，迄今为止仅观察到Lcps。纯化的RoxB Xsp揭示了所有目前已知的橡胶加氧酶的最高比活性4.5U/mg（在23 ° C下），并且对RoxA Xsp的聚异戊二烯裂解效率发挥协同效应。RoxB同源物在几种其它革兰氏阴性橡胶降解物种中被鉴定，指出RoxB在革兰氏阴性细菌中对橡胶生物降解的突出功能。重要性橡胶（聚异戊二烯）的酶促裂解具有高度的环境重要性，因为大量的橡胶废料被永久释放（例如，通过轮胎的磨损）。过去十年的研究已经发现橡胶加氧酶A、RoxA和胶乳清除蛋白（LCP）分别负责革兰氏阴性和革兰氏阳性橡胶降解细菌中疏水性和水不溶性生物聚合物聚（顺式-1，4-异戊二烯）的主要酶攻击。在这里，我们提供的证据表明，第三种类型的橡胶加氧酶存在于革兰氏阴性橡胶降解物种。由于其特性，我们建议命名为RoxB的新型橡胶加氧酶。基因组序列的生物信息学分析表明在其他革兰氏阴性橡胶降解菌中存在roxB同源物。
Only two types of rubber oxygenases, rubber oxygenase (RoxA) and latex clearing protein (Lcp), have been described so far. RoxA proteins (RoxAs) are c-type cytochromes of approximate to 70 kDa produced by Gram-negative rubber-degrading bacteria, and they cleave polyisoprene into 12-oxo-4,8-dimethyltrideca-4,8-diene-1-al (ODTD), a C-15 oligo-isoprenoid, as the major end product. Lcps are common among Gram-positive rubber degraders and do not share amino acid sequence similarities with RoxAs. Furthermore, Lcps have much smaller molecular masses (approximate to 40 kDa), are b-type cytochromes, and cleave polyisoprene to a mixture of C-20, C-25, C-30, and higher oligo-isoprenoids as end products. In this article, we purified a new type of rubber oxygenase, RoxB Xsp (RoxB of Xanthomonas sp. strain 35Y). RoxB Xsp is distantly related to RoxAs and resembles RoxAs with respect to molecular mass (70.3 kDa for mature protein) and cofactor content (2 c-type hemes). However, RoxB Xsp differs from all currently known RoxAs in having a distinctive product spectrum of C20, C25, C30, and higher oligo-isoprenoids that has been observed only for Lcps so far. Purified RoxB Xsp revealed the highest specific activity of 4.5 U/mg (at 23 degrees C) of all currently known rubber oxygenases and exerts a synergistic effect on the efficiency of polyisoprene cleavage by RoxA Xsp. RoxB homologs were identified in several other Gram-negative rubber-degrading species, pointing to a prominent function of RoxB for the biodegradation of rubber in Gram-negative bacteria.IMPORTANCE The enzymatic cleavage of rubber (polyisoprene) is of high environmental importance given that enormous amounts of rubber waste materials are permanently released (e.g., by abrasion of tires). Research from the last decade has discovered rubber oxygenase A, RoxA, and latex clearing protein (Lcp) as being responsible for the primary enzymatic attack on the hydrophobic and water-insoluble biopolymer poly(cis-1,4-isoprene) in Gram-negative and Gram-positive rubber-degrading bacteria, respectively. Here, we provide evidence that a third type of rubber oxygenase is present in Gram-negative rubber-degrading species. Due to its characteristics, we suggest the designation RoxB for the new type of rubber oxygenase. Bioinformatic analysis of genome sequences indicates the presence of roxB homologs in other Gram-negative rubber degraders.