Que L, Lipscomb J D, Münck E, Wood J M
Biochim Biophys Acta. 1977 Nov 23;485(1):60-74. doi: 10.1016/0005-2744(77)90193-0.
Protocatechuate 3,4-dioxygenase (EC 1.13.11.3) from Pseudomonas aeruginosa catalyzes the cleavage of 3,4-dihydroxybenzoate (protocatechuate) into beta-carboxy-cis,cis-muconate. The inhibition constants, Ki, of a series of substrate analogues were measured in order to assess the relative importance of the various functional groups on the substrate. Though important for binding, the carboxylate group is not essential for activity. Compounds with para hydroxy groups are better inhibitors than their meta isomers. Our studies of the enzyme-inhibitor complexes indicate that the 4-OH group of the substrate binds to the active-site iron. Taken together, Mössbauer, EPR, and kinetic data suggest a mechanism where substrate reaction with oxygen is preceded by metal activation of substrate.
来自铜绿假单胞菌的原儿茶酸3,4-双加氧酶（EC 1.13.11.3）催化3,4-二羟基苯甲酸（原儿茶酸）裂解为β-羧基-顺,顺-粘康酸。为了评估底物上各种官能团的相对重要性，测定了一系列底物类似物的抑制常数Ki。虽然羧酸盐基团对于结合很重要，但对于活性并非必不可少。具有对羟基的化合物比其间位异构体是更好的抑制剂。我们对酶-抑制剂复合物的研究表明，底物的4-羟基与活性位点铁结合。综合起来，穆斯堡尔谱、电子顺磁共振和动力学数据表明了一种机制，即底物与氧反应之前先发生底物的金属活化。
