Poster: Late and Moved Abstracts

Abs # 1398: Investigation of the molecular mechanism and regulation of the starch-phosphorylating enzyme GWD

Presenter:	Mikkelsen, René , rem@kvl.dk
Authors	Mikkelsen, René  (A)   Mutenda, Kudzai  (B)   Baunsgaard, Lone  (A)   Blennow, Andreas  (A)
Affiliations:	(A): Plant Biochemistry Laboratory, The Royal Veterinary and Agricultural University, Copenhagen, Denmark (B): Protein Research group, University of Southern Denmark, Odense, Denmark
Web Site:	http://www.place.kvl.dk

A 320 kDa dimeric enzyme, which is involved in the phosphorylation of large glucan polymers (starch) has been investigated. The enzyme belonging to a new family of enzymes is involved in a newly discovered phosphorylation dependant pathway for starch degradation in plants (1;2). The enzyme catalyzes the phosphorylation of starch (a-1,4 and a-1,6 linked glucose units) in the rather unusual dikinase type reaction mechanism using ATP as the phosphate donor. Hence the enzyme is a glucan water dikinase, GWD (3). An interesting property of GWD is that it catalyzes the phosphorylation of the glucose unit at two different positions, C-6 and C-3. It seemingly has a requirement for the presence of a-1,6 linkages but phosphorylates a wide range of long chain a-glucans. Residues involved in phosphoryl transfer and potential enzymatic regulation have been assigned using site-directed mutagenesis and mass spectrometry. (1)Lorberth, R., Ritte, G., Willmitzer, L., and Kossmann, J. (1998) Nature Biotech. 16, 473-477 (2)Blennow, A., Engelsen, S. B., Nielsen, T. H., Baunsgaard, L., and Mikkelsen, R. (2002) Trends in Plant Science 7, 445-450 (3)Ritte, G., Lloyd, J. R., Eckermann, N., Rottmann, A., Kossmann, J., and Steup, M. (2002) Proceedings Of The National Academy Of Sciences Of The United States Of America 99, 7166-7171