tailieunhanh - Báo cáo khoa học: Cleavage of nonphenolic b-1 diarylpropane lignin model dimers by manganese peroxidase from Phanerochaete chrysosporium Evidence for a hydrogen abstraction mechanism

Purified manganese peroxidase (MnP) fromPhanerocha-ete chrysosporiumoxidizes nonphenolicb-1 diarylpropane lignin model compounds in the presence of Tween 80,and in three- to fourfold lower yield in its absence. In thepresence of Tween 80,1-(3¢,4¢-diethoxyphenyl)-1-hydroxy-2-(4¢-methoxyphenyl)propane (I) was oxidized to 3,4-diethoxy-benzaldehyde (II),4-methoxyacetophenone (III) and 1-(3¢,4¢-diethoxyphenyl)-1-oxo-2-(4¢-methoxyphenyl)pro-pane (IV),while only 3,4-diethoxybenzaldehyde (II) and 4-methoxyacetophenone (III) were detected when the reac-tion was conducted in the absence of Tween 80 | Eur. J. Biochem. 270 2 -- 2 2003 FEBS 2003 doi Cleavage of nonphenolic p-1 diarylpropane lignin model dimers by manganese peroxidase from Phanerochaete chrysosporium Evidence for a hydrogen abstraction mechanism G. Vijay B. Reddy 1 Malayam Sridhar2 and Michael H. Gold Department of Biochemistry and Molecular Biology OGI School of Science and Engineering at OHSU Beaverton Oregon USA Purified manganese peroxidase MnP from Phanerocha-ete chrysosporium oxidizes nonphenolic b-1 diarylpropane lignin model compounds in the presence of Tween 80 and in three- to fourfold lower yield in its absence. In the presence of Tween 80 l- 3 4 -diethoxyphenyl -1-hydroxy-2- 4 -methoxyphenyl propane I was oxidized to 3 4-diethoxy-benzaldehyde II 4-methoxyacetophenone III and 1- 3 4 -diethoxyphenyl -1-oxo-2- 4 -methoxyphenyl pro-pane IV while only 3d-diethy. ybza aldehyde II and 4-methoxyacetophenone III were detected when the reaction was conducted in the absence of Tween 80. In contrast to the oxidation of this substrate by lignin peroxidase LiP oxidation of substrates by MnP did not proceed under anaerobic conditions. When the dimer I was deuterated at the a position and subsequently oxidized by MnP in the presence of Tween 80 yields of 34 -diethoxybenzaldehyde 4-methoxyacetophenone remained constant while the yield of the a-keto dimeric product IV decreased by approximately sixfold uggest die involvemont of a hhdroyon abstraction mechanism. MnP also oxidized the a-keto dimeric product IV to yield 3 4-diethoxybenzoic acid V and 4-methoxyacetophenone III in the presence and in lower yield in the absence of Tween 80. When the reaction was performed in the presence of 18O2 ooth pood nets. 3 4-diethoxybenzoic acid and 4-methoxyacetophenone contained one atom of 18O. Finally M11P oxidE ted the sLIbsratee 1- 3 5 -dimethoxyphenyl -1-hydroxy-2- 4 -methoxyphenyl propane IX to yield 3 5-dimethoxybenzaldehyde XI 4-methoxyacetophenone III and 1- 3 5 .

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