Slow-binding inhibition of branching enzyme by the pseudooligosaccharide BAY e4609

Branching enzyme from Escherichia coli is shown to be inhibited by the pseu dooligosaccharide BAY e4609. The mechanism of binding is studied in detail by kinetics using reduced amylose as substrate. Line-weaver-Burk plots sugg est the mechanism of a noncompetitive or slow-binding inhibitor. Further st udies by progress curves and rate of loss of branching activity allows us t o conclude BAY e4609 as being a slow-binding inhibitor of branching enzyme. We discuss how these results parallel the inhibition of alpha-amylase by a carbose and the significance of branching enzyme as belonging to the amylol ytic family. (C) 2000 Academic Press.