Mikolasch Annett, Matthies Anastasia, Lalk Michael, Schauer Frieder
Institute of Microbiology, Ernst-Moritz-Arndt-University, Greifswald, Germany.
Appl Microbiol Biotechnol. 2008 Sep;80(3):389-97. doi: 10.1007/s00253-008-1595-y. Epub 2008 Jul 31.
Fungal laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Pycnoporus cinnabarinus and Myceliophthora thermophila were used as biocatalysts for enzymatic reaction of halogen-, alkyl-, alkoxy-, and carbonyl-substituted p-hydroquinones (laccase substrates) with p-aminobenzoic acid (no laccase substrate). During this reaction, the laccase substrate was oxidized to the corresponding quinones, which react with p-aminobenzoic acid by amination of the laccase substrate. The different substitutions at the hydroquinone substrates were used to prove whether the substituents influence the position of amination and product yields. The cross-coupling of methoxy-p-hydroquinone (alkoxylated) and 2,5-dihydroxybenzaldehyd (carbonyl-substituted) with p-aminobenzoic acid resulted in the formation of one monoaminated product (yield alkoxylated 52%). If monohalogen- or monoalkyl-substituted p-hydroquinones were used as laccase substrates, two monoaminated products (constitution isomers) were formed. The simultaneous formation of two different monoaminated products from the same hydroquinone substrate is the first report for laccase-mediated synthesis of aminated constitution isomers. Depending from the type of substituent of the hydroquinone, the positions of the two monoaminations are different. While the amination at the monoalkylated hydroquinone occurs at the 5- and 6-positions (yield 38%), the amination at monohalogenated hydroquinones was detectable at the 3- and 5-positions (yield 53%). The same product pattern could be achieved if instead of the biocatalyst laccase the chemical catalyst sodium iodate was used as the oxidant. However, the yields were partially much lower (0-45% of the yields with laccase).
来自朱红密孔菌和嗜热毁丝霉的真菌漆酶（苯二酚：氧氧化还原酶，EC 1.10.3.2）被用作生物催化剂，用于使卤素、烷基、烷氧基和羰基取代的对苯二酚（漆酶底物）与对氨基苯甲酸（非漆酶底物）发生酶促反应。在该反应过程中，漆酶底物被氧化为相应的醌，醌通过漆酶底物的胺化作用与对氨基苯甲酸反应。对苯二酚底物上的不同取代基用于证明这些取代基是否会影响胺化位置和产物产率。甲氧基对苯二酚（烷氧基化）和2,5 - 二羟基苯甲醛（羰基取代）与对氨基苯甲酸的交叉偶联反应生成了一种单胺化产物（烷氧基化产率为52%）。如果使用单卤代或单烷基取代的对苯二酚作为漆酶底物，则会形成两种单胺化产物（构造异构体）。从同一对苯二酚底物同时形成两种不同的单胺化产物，这是漆酶介导合成胺化构造异构体的首次报道。根据对苯二酚取代基的类型，两种单胺化的位置不同。单烷基化对苯二酚的胺化发生在5位和6位（产率38%），而单卤代对苯二酚的胺化在3位和5位可检测到（产率53%）。如果使用化学催化剂碘酸钠代替生物催化剂漆酶作为氧化剂，也能得到相同的产物模式。然而，产率部分要低得多（为漆酶产率的0 - 45%）。
