Ohlendorf D H, Lipscomb J D, Weber P C
E. I. du Pont de Nemours and Co., Central Research and Development Department, Wilmington, Delaware 19880-0228.
Nature. 1988 Nov 24;336(6197):403-5. doi: 10.1038/336403a0.
Dioxygenases catalyse the cleavage of molecular oxygen with subsequent incorporation of both oxygen atoms into organic substrates. Some of the best-studied dioxygenases have been isolated from bacteria where they catalyse the critical ring-opening step in the biodegradation of aromatic compounds. These bacterial enzymes generally contain nonheme ferric iron as the sole cofactor. Protocatechuate 3,4-dioxygenase (3,4-PCD) was one of the first such enzymes recognized and catalyses the intradiol cleavage of protocatechuic acid by oxygen to produce beta-carboxy-cis,cis-muconic acid. Previous studies have shown that the 3,4-PCD found in Pseudomonas aeruginosa is an oligomer with a relative molecular mass (Mr) of 587,000 (587K) containing 12 copies each of alpha (22.3K) and beta (26.6K) subunits. The X-ray structure determination of 3,4-PCD reveals the catalytic iron environment required for oxygenolytic cleavage of aromatic rings and also provides a novel holoenzyme assembly with cubic 23(T) symmetry and first examples of mixed beta-barrel domains.
双加氧酶催化分子氧的裂解，随后将两个氧原子都并入有机底物中。一些研究得最透彻的双加氧酶是从细菌中分离出来的，它们在细菌中催化芳香族化合物生物降解过程中的关键开环步骤。这些细菌酶通常含有非血红素铁作为唯一的辅因子。原儿茶酸3,4-双加氧酶（3,4-PCD）是最早被识别的此类酶之一，它催化原儿茶酸通过氧进行间位裂解，生成β-羧基-顺,顺-粘康酸。先前的研究表明，铜绿假单胞菌中的3,4-PCD是一种寡聚体，相对分子质量（Mr）为587,000（587K），包含α（22.3K）和β（26.6K）亚基各12个拷贝。3,4-PCD的X射线结构测定揭示了芳香环氧解裂解所需的催化铁环境，还提供了一种具有立方23(T)对称性的新型全酶组装体以及混合β桶结构域的首个实例。
