Location: Renewable Product Technology ResearchTitle: 2-acylamido analogues of N-acetylglucosamine prime formation of chitin oligosaccharides by yeast chitin synthase 2) Author
Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2014
Publication Date: 5/2/2014
Publication URL: http://handle.nal.usda.gov/10113/60315
Citation: Gyore, J., Parameswar, A.R., Hebbard, C., Oh, Y., Bi, E., Demchenko, A.V., Price, N.P., Orlean, P. 2014. 2-acylamido analogues of N-acetylglucosamine prime formation of chitin oligosaccharides by yeast chitin synthase 2. Journal of Biological Chemistry. 289(18):12835-12841. Interpretive Summary: Chitin is a sugar polymer consisting of N-acetylglucosamine (GlcNAc), and is generally found in the cell walls of fungi or the exoskeleton of insects. Chitin is made by chitin synthase (CS) enzymes, which are also similar to the enzymes used to make cellulose. The yeast CS enzyme transfers one molecule of GlcNAc from UDP-GlcNAc to pre-existing chitin chains, which incrementally extends the chitin chain length. Fungi usually have several CSs, which can be active in different cellular locations and at different times during cell growth and division. In this study we have explored the role of chitin biosynthesis in detail by using an S. cerevisiae yeast strain that expresses a single CS (called Chs2). By using modified GlcNAc sugars (N-propionyl-, N-butanoyl-, and N-glycolyl-glucosamine) we show that formation of chitin requires free GlcNAc. Chs2 can also use the modified GlcNAc sugars to make chitin disaccharides, and these can be elongated with other GlcNAc residues to form longer polymers. Understanding how fungi biosynthesize their chitin cell walls may ultimately allow us to make modified chitins with potentially useful properties as biomaterials.
Technical Abstract: Chitin, a polymer of beta-1,4-linked N-acetylglucosamine (GlcNAc), is a key component of the cell walls of fungi and the exoskeletons of arthropods. Chitin synthases (CSs) transfer GlcNAc from UDP-GlcNAc to pre-existing chitin chains in reactions that are typically stimulated by free GlcNAc. The effect of GlcNAc was probed by using a yeast strain expressing a single chitin synthase, Chs2, by examining formation of chitin oligosaccharides (COs) and insoluble chitin, and by replacing GlcNAc with 2-amido analogues of GlcNAc. Synthesis of COs was strongly dependent on inclusion of GlcNAc in CS incubations, and GlcNAc2 was the major reaction product. Formation of both COs and insoluble chitin was also stimulated by di-N-acetylchitobiose and by N-propionyl-, N-butanoyl-, and N-glycolylglucosamine. Mass spectrometric analyses of the COs made in the presence of 2-amido analogues of GlcNAc showed they contained a single GlcNAc analogue, and one or more additional GlcNAc residues. These results indicate that Chs2 can use certain 2-amido analogues of GlcNAc, and likely free GlcNAc and GlcNAc2 as well, as GlcNAc acceptors in a UDP-GlcNAc-dependent glycosyltransfer reaction. Further, formation of modified disaccharides indicates that CSs can transfer single GlcNAc residues.