Mode of substrate interaction and energetics of carbon-oxygen bond formation of the dopamine beta-monooxygenase reaction.
Mode of substrate interaction and energetics of carbon-oxygen bond formation of the dopamine beta-monooxygenase reaction.
复制标题
多巴胺β-单加氧酶反应的底物相互作用模式和碳-氧键形成的能量学。
DOI：
10.1021/bi990703x
复制
发表时间：
1999
期刊：
影响因子：
2.9
通讯作者：
Alliston,KR
中科院分区：
文献类型：
--
作者：
Wimalasena,K;Alliston,KR
先前的研究表明，多巴胺β-单加氧酶（d - β m； E.C. 1.14.17.1）/1-（2-氨基乙基）-1,4-环己二烯（CHDEA）反应在侧链和环h萃取之间分离，生成侧链羟基化产物2-氨基-1-（1,4-环己二烯）乙醇和芳构化产物苯乙胺，两种途径不交叉。[m] m， K.，和May， S. W.（1989）。111年,2729−2731;Wimalasena， K.和Alliston， K. R.（1995）。117、1220−1224]。我们现在报道，在碳-氧键形成步骤中，反应的环h提取途径进一步分裂，产生环羟基化产物CHDEA-6OH和芳香化产物PEA。环羟基化被证明是立体特异性的，只产生(S)产物。d - β m /CHDEA反应的环羟基化和侧链羟基化的绝对立体专一性表明，酶结合底物的侧链亲氢与苯乙胺底物的芳香环或CHDEA的环己二烯环接近垂直。相对活化能参数表明，环H提取途径在芳构化产物和环羟基化产物之间的分配是由于高能中间体环己二烯基自由基和Cu(II)−O•物质在碳-氧键形成和直接电子转移之间的分配。碳氧键形成的相对较高的激活焓有利度和熵不利度强烈表明，这两种相反的力的临界平衡对于期望的产物形成是必需的。
Previous studies have shown that the dopamine β-monooxygenase (DβM; E.C. 1.14.17.1)/1-(2-aminoethyl)-1,4-cyclohexadiene (CHDEA) reaction partitions between side chain and ring H-abstraction to produce the side-chain-hydroxylated product, 2-amino-1-(1,4-cyclohexadienyl)ethanol, and the aromatized product, phenylethylamine, and that the two pathways do not crossover. [Wimalasena, K., and May, S. W. (1989)J.Am.Chem.Soc.111, 2729−2731; Wimalasena, K., and Alliston, K. R. (1995)J.Am.Chem.Soc.117, 1220−1224]. We now report that the ring H-abstraction pathway of the reaction further partitions to produce the ring hydroxylated product, CHDEA-6OH, and the aromatized product, PEA, at the carbon−oxygen bond formation step. The ring hydroxylation is shown to be stereospecific, exclusively producing the(S)product. The absolute stereospecificity of the ring and side-chain hydroxylations of the DβM/CHDEA reaction suggests that the side-chainpro-Rhydrogen of the enzyme-bound substrate is close to perpendicular to the aromatic ring of the phenylethylamine substrate or cyclohexadiene ring of CHDEA. The relative activation energy parameters suggest that the partitioning of the ring H abstraction pathway between aromatized and ring hydroxylated products is due to the partitioning of the high-energy intermediates, the cyclohexadienyl radical and the Cu(II)−O•species, between carbon−oxygen bond formation and direct electron transfer. The relatively high activation enthalpic favorability and entropic unfavorability for the carbon−oxygen bond formation strongly suggest that the critical balancing of these two opposing forces is mandatory for the desired product formation.