通过生物素及其维生素类似物的衍射研究提出的羧基生物素转运机制。
Carboxybiotin translocation mechanisms suggested by diffraction studies of biotin and its vitamers.
作者信息
DeTitta G T, Parthasarathy R, Blessing R H, Stallings W
出版信息
Proc Natl Acad Sci U S A. 1980 Jan;77(1):333-7. doi: 10.1073/pnas.77.1.333.
Biotin is a coenzyme that fixes CO2 for transfer in a family of carboxylase, decarboxylase, and transcarboxylase enzymes. Their enzyme reactions involve two basic steps during which a carboxybiotinyl intermediate forms at one site and translocates to a second (distinct) site for CO2 transfer. Our diffraction studies of biotin and its vitamers suggest that translocation involves rotation about one, or at most two, bonds in biotin's valeryl chain. The rotations are energetically economical gauche in equilibrium trans rotations about the two valeryl bonds nearest the biotin bicyclic ring. They move a carbon atom of a CO2 moiety bound at N-1' approximately 7 A, a distance in accord with spectroscopic measurements of one of the biotin enzymes. From our studies we infer that sulfur in biotin imparts to the valeryl chain a conformational variability necessary for bond rotation and, hence, translocation between catalytic sites.
生物素是一种辅酶，可在羧化酶、脱羧酶和转羧酶家族中固定二氧化碳以便进行转移。它们的酶促反应包括两个基本步骤，在此过程中，羧基生物素中间体在一个位点形成并转移至第二个（不同的）位点进行二氧化碳转移。我们对生物素及其维生素类似物的衍射研究表明，转移涉及生物素戊酰基链中一个或最多两个键的旋转。这些旋转在能量上是经济的，是围绕最靠近生物素双环的两个戊酰基键的平衡反式旋转中的gauche旋转。它们使结合在N-1'处的二氧化碳部分的一个碳原子移动约7埃，这一距离与其中一种生物素酶的光谱测量结果一致。从我们的研究中我们推断，生物素中的硫赋予戊酰基链构象变异性，这对于键的旋转以及因此在催化位点之间的转移是必要的。
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