New Studies on Amylosucrase, a Bacterial α-d-Glucosylase That Directly Converts Sucrose to a Glycogen-like α-Glucan

Amylosucrase(EC 2.4.1.4)was solubilized and purified more than lOO-fold from Neisseria perjlava cells.Preparations had a specific activity of about 3 i.u. per mg of protein, were free of maltase and oc-glucan phosphorylase activity, and converted sucrose to an amylaceous a-glucan, fructose, and minor amounts of maltosaccharides (Keq = 33, AG" = -2.1 Cal).Sugar nucleotide mediation was absent.Added UDP or ADP did not affect the conversion rate, or provide UDP-or ADP-[14C]glucose from [i4C]sucrose even when polymerization was prevented by a-amylase.The a-glucan formed from sucrose was glycogen-like (e.g.48% hydrolyzed to maltose by P-amylase).The branches may be produced in the usual way, assuming the amylosucrase preparations were contaminated with a dextrinyl transferring (branching) enzyme.It is possible, however, that amylosucrase itself may produce the entire glucan structure by a distinctive process involvingCu-D-&COSyl