期刊
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
卷 66, 期 5, 页码 1206-1213出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jafc.7b05018
关键词
biodegradation; biotransformation; catalytic site accessibility; polycyclic aromatic hydrocarbon; ring-hydroxylating dioxygenase; Sphingobium sp FB3; substrate specificity
资金
- National Key R&D Program of China [2016YFD0800600]
- U.S. National Institutes of Health Research Centers in Minority Institutions Program [8 G12 MD007601]
- U.S. National Science Foundation Career Award [1350555]
- China Agricultural University scholarship
- Direct For Biological Sciences [1833181] Funding Source: National Science Foundation
Burning of agricultural biomass generates polycyclic aromatic hydrocarbons (PAHs) including the carcinogen benzo[a]pyrene, of which the catabolism is primarily initiated by a ring-hydroxylating dioxygenase (RHD). This study explores catalytic site accessibility and its role in preferential catabolism of some PAHs over others. The genes fInA1f, fInA2f, flnA3, and flnA4, encoding the oxygenase alpha and beta subunits, ferredoxin, and ferredoxin reductase, respectively, of the RHD enzyme complex (FlnA) were cloned from Sphingobium sp. FB3 and coexpressed in E. coli BL21. The FlnA effectively transformed fluoranthene but not benzo[a]pyrene. Substitution of the bulky phenylalanine-223 by leucine reduces the steric constraint in the substrate entrance to make the catalytic site of FlnA more accessible to large substrates, as visualized by 3D modeling, and allows the FlnA mutant to efficiently transform benzo[a]pyrene. Accessibility of the catalytic site to PAHs is a mechanism of RHD substrate specificity. The results shed light on why some PAHs are more recalcitrant than others.
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