Institute of Microbiology, Ernst-Moritz-Arndt-University of Greifswald, Friedrich-Ludwig-Jahn Straße 15, 17487, Greifswald, Germany,
Appl Microbiol Biotechnol. 2014 Feb;98(4):1609-20. doi: 10.1007/s00253-013-4984-9. Epub 2013 May 29.
Laccases are able to mediate both cleavage and synthesis processes. The basis for this dual reaction capability lies in the property of the enzyme laccase to oxidize phenolic, and to some extent non-phenolic substances, to reactive radicals which can undergo on the one hand separations of small substitutents or large molecule parts from the parent compound and on the other hand coupling reactions with other radicals or molecules which are not themselves oxidizable by laccase. The cleavage of the non-phenolic compound 4-morpholinoaniline as well as the deamination of 4-aminophenol and the dechlorination of 4-chlorophenol resulted in the formation of 1,4-hydroquinone which is immediately oxidized by laccase to 1,4-benzoquinone. The formation of the 1,4-hydroquinone/1,4-benzoquinone is the rate limiting step for the synthesis of the heteromolecular dimers and trimers composed of 1,4-benzoquinone and one or two molecules of morpholine. In addition to the synthesis of new compounds from the cleavage products, 4-morpholinoaniline polymerized probably via azo groups and C-N bonds to a homomolecular dimer and trimer. Similarities and differences in cleavage and synthesis reactions catalyzed by the low redox potential laccase of Myceliophthora thermophila (0.46 V) and the high redox potential laccase of Pycnoporus cinnabarinus (0.79 V) were determined. In addition, the dependency of the cleavage and synthesis efficiencies on the (a) structure and redox potential of the laccase, (b) structure and redox potential of the substrate, (c) pH value of the buffer used, (d) incubation temperature, (e) solvent concentration, and (f) laccase activity is discussed in general.
漆酶能够介导裂解和合成过程。这种双重反应能力的基础在于酶漆酶氧化酚类，在某种程度上氧化非酚类物质，形成活性自由基，这些自由基一方面可以将小分子取代基或大分子部分从母体化合物中分离出来，另一方面可以与其他不是自身被漆酶氧化的自由基或分子发生偶联反应。非酚类化合物 4-吗啉苯胺的裂解，以及 4-氨基酚的脱氨和 4-氯苯酚的脱氯，导致 1,4-对苯二酚的形成，而 1,4-对苯二酚立即被漆酶氧化为 1,4-苯醌。1,4-对苯二酚/1,4-苯醌的形成是由 1,4-苯醌和一个或两个吗啉分子组成的异分子二聚体和三聚体合成的限速步骤。除了从裂解产物中合成新化合物外，4-吗啉苯胺可能通过偶氮基团和 C-N 键聚合形成同分子二聚体和三聚体。测定了低氧化还原电位漆酶（0.46 V）和高氧化还原电位漆酶（0.79 V）催化的裂解和合成反应的相似性和差异。此外，还讨论了裂解和合成效率对（a）漆酶的结构和氧化还原电位、（b）底物的结构和氧化还原电位、（c）所用缓冲液的 pH 值、（d）孵育温度、（e）溶剂浓度和（f）漆酶活性的依赖性。
