Synthesis and characterization of model compounds of the lysine tyrosyl quinone cofactor of lysyl oxidase
Synthesis and characterization of model compounds of the lysine tyrosyl quinone cofactor of lysyl oxidase
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DOI：
10.1021/ja0214274
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发表时间：
2003-05-21
影响因子：
15
通讯作者：
Klinman, JP
中科院分区：
文献类型：
--
作者：
Mure, M;Wang, SX;Klinman, JP
合成了赖氨酰氧化酶（LOX）的LTQ（赖氨酸酪氨酰醌）辅因子的模型化合物4-正丁基氨基-5-乙基-1，2-苯醌（1（ox））。在pH 7时，1（ox）在504 nm处具有λ（max），并且与TPQ（2，4，5-三羟基苯基苯胺醌）模型化合物4（其为共振稳定的单阴离子）相反，1（ox）作为中性邻醌存在。尽管存在这些结构差异，1（ox）和4具有相同的氧化还原电位（ca。-180 mV vs SCE）。报道了1（ox）（2）的苯肼加成物的结构，并用二维核磁共振谱表明亲核加成的位置在C-1位。1（ox）和4、2和11的苯肼加合物的紫外-可见光谱pH滴定分别揭示了在碱性pH下具有相同pK（a）（类似于11.8）的λ（max）的类似红移。相反，在酸性pH条件下λ（max）的红移产生不同的pK（a）值（2的2.12对11的-0.28），提供了区分LTQ与TPQ的方法。原位生成的4-乙基-1，2-苯醌和伯胺之间的反应得到的混合物的产品，表明蛋白质环境必须发挥重要作用，在LTQ生物合成的指导亲核加成的C-氨基基团的赖氨酸残基的C-4位置的推定多巴醌中间体。邻醌和丁胺（3-正丁基氨基-5-乙基-1，2-苯醌，13）之间的1，6-加合物的表征证实了LTQ作为1，4-加成产物的归属。
4-n-Butylamino-5-ethyl-1,2-benzoquinone (1(ox)) has been synthesized as a model compound for the LTQ (lysine tyrosyl quinone) cofactor of lysyl oxidase (LOX). At pH 7, 1(ox) has a lambda(max) at 504 nm and exists as a neutral o-quinone in contrast to a TPQ (2,4,5-trihydroxyphenylaianine quinone) model compound, 4, which is a resonance-stabilized monoanion. Despite these structural differences 1(ox) and 4 have the same redox potential (ca. -180 mV vs SCE). The structure of the phenylhydrazine adduct of 1(ox) (2) is reported, and 2D NMR spectroscopy has been used to show that the position of nucleophilic addition is at C-1. UV-vis spectroscopic pH titration of phenylhydrazine adducts of 1(ox) and 4, 2, and 11, respectively, reveals a similar red shift in lambda(max) at alkaline pH with the same pK(a) (similar to11.8). In contrast, the red shift in lambda(max) at acidic pH conditions yields different pK(a) values (2.12 for 2 vs -0.28 for 11), providing a means to distinguish LTQ from TPQ. Reactions between in situ generated 4-ethyl-1,2-benzoquinone and primary amines give a mixture of products, indicating that the protein environment must play an essential role in LTQ biogenesis by directing the nucleophilic addition of the c-amino group of a lysine residue to the C-4 position of a putative dopaquinone intermediate. Characterization of a 1,6-adduct between an o-quinone and butylamine (3-n-butylamino-5-ethyl-1,2-benzoquinone, 13) confirms the assignment of LTQ as a 1,4-addition product.