Improved Manganese-Oxidizing Activity of DypB, a Peroxidase from a Lignolytic Bacterium

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• 作者：Rahul Singh ; Jason C. Grigg ; Wei Qin ; John F. Kadla ; Michael E. P. Murphy ; Lindsay D. Eltis
• 刊名：ACS Chemical Biology
• 出版年：2013
• 出版时间：April 19, 2013
• 年：2013
• 卷：8
• 期：4
• 页码：700-706
• 全文大小：342K
• 年卷期：v.8,no.4(April 19, 2013)
• ISSN：1554-8937

文摘

DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn²⁺), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme鈥檚 apparent k_cat and k_cat/K_m values for Mn²⁺ by 80- and 15-fold, respectively. A 2.2 脜 resolution X-ray crystal structure of the N246A variant revealed the Mn²⁺ to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn²⁺-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant鈥檚 high K_m for Mn²⁺ (17 卤 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin.