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Carbohydrate-active enzymes for forest industrial fibre engineering

Published 2000-01-13

In April 2001 Professor Tuula Teeri, researcher at the Royal Institute of Technology, KTH in Stockholm has received an Institutional Grant for cooperation with Dr David Cullen, University of Wisconsin. The annual grant of SEK 250 000 is intended for cooperation within ’Functional genomics of wood fibre modification’.

Pulp and paper production is of vital economical interest both in Sweden and in the USA. The industry is highly competitive, capital intensive and faces increasing environmental requirements. Biotechnology offers alternative processes and improved raw materials for the pulp and paper industries. Microbial hydrolytic enzymes form the basis of current green technology in the industry and the revolution in genomics offers long-term gains on the quality and quantity of the raw materials. In particular, plants constitute a new and largely unexplored source of fiber-active enzymes that work in the synthetic direction and thus be used to upgrade fiber properties. The general objective of the current collaboration is to carry out comparative enzyme discovery and characterization of carbohydrate-active enzymes in three different organisms: a tree, a filamentous fungus and a bacterium. The American partners, Dr Dan Cullen from the University of Wisconsin, and Professor David Wilson from the Cornell University are experts on the fungal and bacterial enzyme systems from Phanerochaete chrysosporium and Thermobifida fusca. The Swedish partner, Professor Tuula Teeri from the Royal Institute of Technology in Stockholm focuses on the enzymology of wood fiber biosynthesis in hybrid aspen, Populus tremula x tremuloides.

As a concrete example of the collaborative efforts within this project, we have characterized cellulose-degrading enzymes from all the three organisms. The bacterial enzymes are secreted to the culture medium while the fungal and the plant enzymes are membrane-bound (see below 1,2). Several large aromatic amino acid side chains have been previously identified in the active site of the bacterial cellulase (W256, W313, W209) (Figure 1). These side chains, which form direct interactions with the substrate, were found to be missing in the corresponding plant enzyme (G371, Q443, T326). This finding provides a molecular explanation for the reduced activity of the plant enzyme, which is required for subtle modification instead of complete degradation of the plant cell wall.

Figure 1. Molecular model of the active sites of a bacterial (pink) and a plant endoglucanase (green) in complex with the substrate (red-and-yellow).

Professor Tuula Teeri

1.Van den Wymelenberg A, Denman S, Dietrich D, Bassett J, Yu X, Atalla R, Predki P, Rudsander U, Teeri TT, Cullen D (2002) Transcript analysis of Genes Encoding a Family 61 Endoglucanase and a Putative Membrane-anchored Family 9 Glycosyl Hydrolase from Phanerochaete chrysosporium. Appl Environ Microbiol. 68:5765-5768.

2.Master E, Rudsander U, Zhou W, Henriksson H, Divne C, Denman S, Wilson D, Teeri, TT. (2004) Recombinant Expression and Enzymatic Characterization of PttCel9A, a KOR Homolog from Populus tremula x tremuloides. Sumbitted.



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