MOLECULAR-STRUCTURE OF BIOTIN - RESULTS OF 2 INDEPENDENT CRYSTAL-STRUCTURE INVESTIGATIONS
MOLECULAR-STRUCTURE OF BIOTIN - RESULTS OF 2 INDEPENDENT CRYSTAL-STRUCTURE INVESTIGATIONS
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DOI：
10.1021/ja00423a045
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发表时间：
1976-01-01
影响因子：
15
通讯作者：
DONOHUE, J
中科院分区：
文献类型：
--
作者：
DETITTA, GT;EDMONDS, JW;DONOHUE, J
d-(+)-生物素是生物系统中负责二氧化碳固定和转移的辅酶，通过x射线衍射技术在两个实验室独立确定了d-(+)-生物素的三维晶体。根据辅酶的亲核活化模式，对两种测定结果进行了比较和讨论。特别相关的可能是脲基羰基O作为强氢键受体的参与（O.cntdot. cntdot. cntdot. cntdot.O距离2.54 . ang .），这可能导致观察到的脲基羰基键延长至1.25 . ang。羰基C-N键缩短至1.33和1.35 ang。这些结果表明，在脲基内的电子电荷部分离域，并支持通过极化机制提出的激活。一个紧密的分子内非键接触涉及近戊基链的N原子可能排除从分子的那一边羧基化。
The 3-dimensional crystal of d-(+)-biotin, the coenzyme responsible for the fixation and transfer of CO2 in biological systems, was determined by x-ray diffraction techniques in 2 laboratories independently. The results of the 2 determinations are compared and discussed in terms of the mode of nucleophilic activation of the coenzyme. Of particular relevance may be the participation of the ureido carbonyl O as acceptor of a strong H-bond (O.cntdot..cntdot..cntdot.O distance 2.54 .ANG.) which may cause the observed lengthening of the ureido carbonyl bond to 1.25 .ANG. and shortening of the carbonyl C-N bonds to 1.33 and 1.35 .ANG.. These results suggest a partial delocalization of the electronic charge within the ureido group, and are supportive of a proposed activation via polarization mechanism. A close intramolecular nonbonded contact involving the N atom proximal to the valeryl chain probably precludes carboxylation from that side of the molecule.