08/06/2014
Evolution of Substrate Specificity in Bacterial Lytic Polysaccharide Monooxygenases
The Science
Cellulose is one of the most abundant polysaccharides in nature and one of the primary components of plant cell walls. The biofuels industry has devoted significant efforts to establish processes to convert these energy-rich molecules into sugars that can be fermented into biofuels or other bioproducts. However, the hydrolysis of these polysaccharides, a key step in converting them to biofuels, is difficult due to their crystalline structure, the stability of some bonds within their structure, and how closely they are associated with structure-modifying molecules such as hemicellulose and lignin. Efficient hydrolysis requires a cocktail of different enzymes. Enzymes capable of hydrolyzing these polymers have been identified in various organisms, especially bacteria and fungi, but the pathways for deconstruction of certain polysaccharides, such as cellulose and chitin, are only partially understood. Researchers at the Department of Energy’s Great Lakes Bioenergy Research Center analyzed the sequences, structures, and evolution of two families of enzymes, fungal AA9 and bacterial AA10, both lytic polysaccharide monooxygenases (LPMOs), to understand the factors that influence substrate specificity in these families and to characterize the selective pressures that may have led to their functional diversification. Their sequence similarity suggests that both families share a distant common ancestor and that certain clades within the AA10 family are specialized for different substrates, while others went through a diversifying selection at surface-exposed regions of the protein. Understanding the diversity of these lignocellulosic-degrading enzymes in nature provides information that can help improve enzymatic cocktails used in the biofuels industry.
BER Program Manager
Shing Kwok
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]
References
Book, A. J., R. M. Yennamalli, T. E. Takasuka, C. R. Currie, G. N. Phillips, and B. G. Fox. 2014. “Evolution of Substrate Specificity in Bacterial AA10 Lytic Polysaccharide Monooxygenases,” Biotechnology for Biofuels 7,109. DOI: 10.1186/1754-6834-7-109.