A structural explanation for the mechanism and specificity of plant branching enzymes I and IIb.
A structural explanation for the mechanism and specificity of plant branching enzymes I and IIb.
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DOI：
10.1016/j.jbc.2021.101395
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发表时间：
2022-01
期刊：
影响因子：
--
通讯作者：
Geiger JH
中科院分区：
文献类型：
--
作者：
Gavgani HN;Fawaz R;Ehyaei N;Walls D;Pawlowski K;Fulgos R;Park S;Assar Z;Ghanbarpour A;Geiger JH
分支酶（BE）在淀粉和糖原的生物合成中是必不可少的，并且在决定这些聚合物的精细结构中起关键作用。这些BE的底物是长的碳水化合物链，其通过酶表面上的多个结合位点与这些酶相互作用。通过控制支链长度分布，BE可以介导淀粉和糖原部分的生理特性;然而，这种特异性的机制和结构决定因素仍然是神秘的。在这项研究中，我们确定了一个大的十二碳糖结合表面水稻BE I（BEI），达到从外部的活性位点的酶的活性位点。诱变活性测定证实了该结合位点在酶催化中的重要性，由此我们得出结论，它可能是受体链结合位点。来自蓝杆藻的BE和来自水稻的BE 1的结构的比较使我们能够模拟供体结合位点的位置。我们还确定了两个可能与供体链相互作用的环，其序列在植物BE 1（倾向于转移较长的链）和BEIIb（专门转移短得多的链）之间存在分歧。当这些环的序列与BEIIb序列交换时，水稻BE 1也成为短链转移酶，证明了这些环在特异性中发挥的关键作用。总之，这些结果提供了一个更完整的图片的结构，选择性和活性的BE。
Branching enzymes (BEs) are essential in the biosynthesis of starch and glycogen and play critical roles in determining the fine structure of these polymers. The substrates of these BEs are long carbohydrate chains that interact with these enzymes via multiple binding sites on the enzyme’s surface. By controlling the branched-chain length distribution, BEs can mediate the physiological properties of starch and glycogen moieties; however, the mechanism and structural determinants of this specificity remain mysterious. In this study, we identify a large dodecaose binding surface on rice BE I (BEI) that reaches from the outside of the active site to the active site of the enzyme. Mutagenesis activity assays confirm the importance of this binding site in enzyme catalysis, from which we conclude that it is likely the acceptor chain binding site. Comparison of the structures of BE from Cyanothece and BE1 from rice allowed us to model the location of the donor-binding site. We also identified two loops that likely interact with the donor chain and whose sequences diverge between plant BE1, which tends to transfer longer chains, and BEIIb, which transfers exclusively much shorter chains. When the sequences of these loops were swapped with the BEIIb sequence, rice BE1 also became a short-chain transferring enzyme, demonstrating the key role these loops play in specificity. Taken together, these results provide a more complete picture of the structure, selectivity, and activity of BEs.
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影响因子：
5.5
作者：
Popov, D.;Buleon, A.;Riekel, C.
通讯作者：
Riekel, C.
影响因子：
3.1
作者：
BOYER, CD;PREISS, J
通讯作者：
PREISS, J
影响因子：
4.8
作者：
Hamada, S;Ito, H;Matsui, H
通讯作者：
Matsui, H
DOI：
10.1007/s11427-008-0120-y
发表时间：
2008-10-01
期刊：
SCIENCE IN CHINA SERIES C-LIFE SCIENCES
影响因子：
--
作者：
Lue Bing;Guo ZhiGang;Liang JianSheng
通讯作者：
Liang JianSheng
影响因子：
4.3
作者：
Noguchi, Junji;Chaen, Kimiko;Kimura, Makoto
通讯作者：
Kimura, Makoto