A-l,4-glucan, chain

A-chains these are short (20-40 glucose units) and have no branches. They form double helices with adjacent terminal, unbranched a-(l->4)-glucan chains. The helices are usually taken as left-handed, but... 

Matheson N.K., Caldwell R.A., a(l-4) Glucan chain disposition in models of a(l )(l-6) glucans Comparison with structural data for mammalian glycogen and waxy amylopectin, Carbohydr. Polym., 40,1999, 191-209. 

SCHEME 1. Action of a-(l 4)-glucan lyase on floridean starch (the monosaccharide derivatives, which are split from the nonreducing ends of the polysaccharide chains probably in the form of 2-hydroxyglucal, are tautomerized to the more stable 1,5-anhydro-D-fructose, 5). 

The most extensively used transferase in the field of polymer science is phosphorylase (systematic name (1—>4)-a-D-glucan phosphate a-D-glucosyltransferase EC 2.4.1.1). While this enzyme is responsible for the depolymerization of linear a-(l—>4) glycosidic chains in vivo it can also be used to synthesize linear a-(l— 4) glycosidic chains (amylose) in vitro. 

A., Atomi, H., and Nidetzky, B. (2009) Short-chain a-l,4-glucan phospho-rylase having a truncated N-terminal domain functional expression and characterization of the enzyme from Sulfolobus solfataricus. Biochim. Bio-phys. Acta, 1794, 1709-1714. 

Cellulose synthesis by Acetobacter is a complex process and involves (a) the polymerization of glucose residues into linear ) -l,4-glucan chains, (b) the extra-cellullar secretion of these linear chains, and (c) crystallization of the glucan chains into hierarchically composed ribbons [2]. 

Polymerization of the 3-l,4-glucan chain is catalyzed by cellulose synthase enzymes. All known cellulose synthases are family 2 processive glycosyltrans-ferases, a ubiquitous family of enzymes which also includes chitin synthases, hyaluronan synthases, and NodC proteins (Saxena et al. 2001). Cellulose synthase sequences share a highly conserved catalytic region containing the D, D, D,... 

Bacterial cellulose synthesis by G. xylinus starts with the production of individual 3-(l->4) chains between the outer and plasma membranes of the bacterial cell. A single G. xylinus cell may polymerize up to 200 000 glucose molecules per second into (3-(l->4) glucan chains, followed by their release outwards through pores in the cell surface [ 14]. BC chains then assemble into protofibrils, with approximately 2-4 nm of diameter, that... 

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