Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States of America; Department of Biomedical Engineering, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States of America.
Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States of America; Department of Chemistry, Reed College, 3203 SE Woodstock Blvd, Portland, OR 97202, United States of America.
J Inorg Biochem. 2022 Jun;231:111780. doi: 10.1016/j.jinorgbio.2022.111780. Epub 2022 Feb 28.
An important question is whether consensus mechanisms for copper monooxygenase enzymes such as peptidylglycine monooxygenase (PHM) and dopamine β-monooxygenase (DBM) generated via computational and spectroscopic approaches account for important experimental observations. We examine this question in the light of recent crystallographic and QMMM reports which suggest that alternative mechanisms involving an open to closed conformational cycle may be more representative of a number of experimental findings that remain unaccounted for in the canonical mononuclear mechanisms. These include (i) the almost negligible reactivity of the catalytic copper site (CuM) with oxygen in the absence of substrate, (ii) the carbonyl chemistry and in particular the substrate-induced activation exemplified by the lowered CO stretching frequency, (iii) the peroxide shunt chemistry which demands an intermediate that facilitates equilibrium between a Cu(II)-peroxo state and a Cu(I)-dioxygen state, and (iv) clear evidence for both closed and open conformational states in both PHM and DBM. An alternative mechanism involving a dinuclear copper intermediate formed via an open to closed conformational transition appears better able to accommodate these experimental observations, as well as being shown by QMMM methodologies to be energetically feasible. This suggests that future experiments should be designed to distinguish between these competing mechanisms and the factors that govern the oxygen reactivity of the copper centers. In particular, determining how oxygen reactivity is activated by binding of substrate, should be considered an important new challenge.
一个重要的问题是，通过计算和光谱学方法产生的铜单加氧酶（如肽基甘氨酸单加氧酶（PHM）和多巴胺 β-单加氧酶（DBM））的共识机制是否可以解释重要的实验观察结果。我们根据最近的晶体学和 QMMM 报告来研究这个问题，这些报告表明涉及开环到闭环构象循环的替代机制可能更能代表许多实验发现，这些发现目前无法用经典的单核机制来解释。这些发现包括：（i）在没有底物的情况下，催化铜位（CuM）与氧的几乎可以忽略不计的反应性，（ii）羰基化学，特别是底物诱导的激活，表现在降低的 CO 伸缩频率，（iii）过氧化物分流化学，这需要一种中间体来促进 Cu(II)-过氧态和 Cu(I)-氧态之间的平衡，以及（iv）在 PHM 和 DBM 中都有明确的闭和开构象态的证据。一种涉及通过开环到闭环构象转变形成的双核铜中间体的替代机制似乎更能适应这些实验观察结果，而且 QMMM 方法学也证明其在能量上是可行的。这表明未来的实验应该设计用于区分这些竞争机制和控制铜中心氧反应性的因素。特别是，确定氧反应性如何通过结合底物而被激活，应该被视为一个重要的新挑战。
