Location: Bioenergy ResearchTitle: Structure of the catalytic domain of glucuronoyl esterase Cip2 from Hypocrea jecorina Author
Submitted to: Proteins: Structure, Function, and Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2011
Publication Date: 5/16/2011
Citation: Pokkuluri, P.R., Duke, N.E., Wood, S.J., Cotta, M.A., Li, X., Biely, P., Schiffer, M. 2011. Structure of the catalytic domain of glucuronoyl esterase Cip2 from Hypocrea jecorina. Proteins: Structure, Function, and Genetics. 79(8):2588-2592. Interpretive Summary: Continued development of a renewable, agriculture-based system for production of fuels (such as ethanol) and chemicals to replace petroleum will require the recruitment of new renewable materials to add to the current corn starch based feedstocks. These materials will include agricultural residues like straws and corn stover and new dedicated energy crops such as switchgrass. One of the obstacles to converting massive quantities of these inexpensive feedstocks to products is the inefficiency and/or high cost of processing plant biomass into simple fermentable sugars. Lignin is a polymer also present in plant biomass and is considered the ‘‘enemy’’ for production of ethanol from plant biomass, because it interferes with the breakdown of biomass and pretreatment to remove lignin is an expensive step in the conversion process. We recently discovered a group of enzymes, called glucuronoyl esterases, which could be important in lignin removal. In the current work, we determined the structure of the glucuronoyl esterase Cip2 from a commercial fungus. The results reported will help us to understand the role of this type of enzyme in plant cell wall biodegradation and efficient bioconversion of cellulosic biomass into biofuels and bioproducts.
Technical Abstract: The structure of the catalytic domain of glucuronoyl esterase Cip2 from the fungus Hypocrea jecorina was determined at a resolution of 1.9 Angstroms. This is the first structure of the newly established carbohydrate esterase family 15. The structure has revealed the residues Ser278–His411–Glu301 present in a triad arrangement as the active site. Ser278 is present in the novel consensus sequence GCSRXG reported earlier in the members of CE-15 family14. The active site is exposed on the surface of the protein which has implications for the ability of the enzyme to hydrolyze ester bonds of large substrates. Efforts are underway to obtain crystals of Cip2_GE complexed with inhibitor and synthetic substrates. The activity of the glucuronoyl esterase could play a significant role in plant biomass degradation as its expected role is to separate the lignin from hemicelluloses by hydrolysis of the ester bond between 4-O-methyl-D-glucuronic acid moieties of glucuronoxylans and aromatic alcohols of lignin.