Pfeifer F, Trüper H G, Klein J, Schacht S
DMT-Gesellschaft für Forschung und Prüfung mbH, Institut für chemische Umwelttechnologie, Essen, Germany.
Arch Microbiol. 1993;159(4):323-9. doi: 10.1007/BF00290914.
2,3-Dihydroxybiphenyl dioxygenase from Pseudomonas cepacia Et 4 was found to catalyze the ring fission of 2,3-dihydroxydiphenylether in the course of diphenylether degradation. The enzyme was purified and characterized. It had a molecular mass of 240 kDa and is dissociated by SDS into eight subunits of equal mass (31 kDa). The purified enzyme was found to be most active with 2,3-dihydroxybiphenyl as substrate and showed moderate activity with 2,3-dihydroxydiphenylether, catechol and some 3-substituted catechols. The Km-value of 1 microM for 2,3-dihydroxydiphenylether indicated a high affinity of the enzyme towards this substrate. The cleavage of 2,3-dihydroxydiphenylether by 2,3-dihydroxybiphenyl dioxygenase lead to the formation of phenol and 2-pyrone-6-carboxylate as products of ring fission and ether cleavage without participation of free intermediates. Isotope labeling experiments carried out with 18O2 and H2(18)O indicated the incorporation of 18O from the atmosphere into the carboxyl residue as well as into the carbonyl oxygen of the lactone moiety of 2-pyrone-6-carboxylate. Based on these experimental findings the reaction mechanism for the formation of phenol and 2-pyrone-6-carboxylate is proposed in accordance with the mechanism suggested by Kersten et al. (1982).
已发现洋葱伯克霍尔德菌Et 4中的2,3-二羟基联苯双加氧酶在二苯醚降解过程中催化2,3-二羟基二苯醚的开环反应。该酶经过了纯化和特性鉴定。它的分子量为240 kDa，在SDS作用下解离为八个等质量的亚基（31 kDa）。发现纯化后的酶以2,3-二羟基联苯为底物时活性最高，对2,3-二羟基二苯醚、儿茶酚和一些3-取代儿茶酚表现出中等活性。2,3-二羟基二苯醚的Km值为1 microM，表明该酶对该底物具有高亲和力。2,3-二羟基联苯双加氧酶催化2,3-二羟基二苯醚的裂解，生成苯酚和2-吡喃酮-6-羧酸盐，作为开环和醚裂解的产物，无需游离中间体的参与。用18O2和H2(18)O进行的同位素标记实验表明，大气中的18O掺入到羧基残基以及2-吡喃酮-6-羧酸盐内酯部分的羰基氧中。基于这些实验结果，根据Kersten等人（1982年）提出的机制，提出了苯酚和2-吡喃酮-6-羧酸盐形成的反应机制。
