期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 293, 期 14, 页码 4955-4968出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA117.001268
关键词
bacterial metabolism; enzyme mechanism; enzyme structure; lignin degradation; Escherichia coli (E; coli); beta-aryl ether; deglutathionylation; glutathione S-transferases; Novosphingobium aromaticivorans; Nu-class
资金
- Federal funds from NCI, National Institutes of Health (NIH) [ACB-12002]
- NIGMS, NIH [AGM-12006, P41-GM103311]
- DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]
- NIH-Office of Research Infrastructure Programs High-End Instrumentation Grant [1S10OD012289-01A1]
As a major component of plant cell walls, lignin is a potential renewable source of valuable chemicals. Several sphingomonad bacteria have been identified that can break the -aryl ether bond connecting most phenylpropanoid units of the lignin heteropolymer. Here, we tested three sphingomonads predicted to be capable of breaking the -aryl ether bond of the dimeric aromatic compound guaiacylglycerol--guaiacyl ether (GGE) and found that Novosphingobium aromaticivorans metabolizes GGE at one of the fastest rates thus far reported. After the ether bond of racemic GGE is broken by replacement with a thioether bond involving glutathione, the glutathione moiety must be removed from the resulting two stereoisomers of the phenylpropanoid conjugate -glutathionyl--hydroxypropiovanillone (GS-HPV). We found that the Nu-class glutathione S-transferase NaGST(Nu) is the only enzyme needed to remove glutathione from both (R)- and (S)-GS-HPV in N. aromaticivorans. We solved the crystal structure of NaGST(Nu) and used molecular modeling to propose a mechanism for the glutathione lyase (deglutathionylation) reaction in which an enzyme-stabilized glutathione thiolate attacks the thioether bond of GS-HPV, and the reaction proceeds through an enzyme-stabilized enolate intermediate. Three residues implicated in the proposed mechanism (Thr(51), Tyr(166), and Tyr(224)) were found to be critical for the lyase reaction. We also found that Nu-class GSTs from Sphingobium sp. SYK-6 (which can also break the -aryl ether bond) and Escherichia coli (which cannot break the -aryl ether bond) can also cleave (R)- and (S)-GS-HPV, suggesting that glutathione lyase activity may be common throughout this widespread but largely uncharacterized class of glutathione S-transferases.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据