Truncation of the amino terminus of branching enzyme changes its chain transfer pattern.
Previous work has reported the production of an Escherichia coli branching enzyme with a 112-residue deletion at the amino terminal by limited proteolysis. Here, we study the chain transfer pattern of this enzyme. Gel-permeation chromatography of in vitro branched amylose shows that the truncated branching enzyme transfers fewer short chains (degree of polymerization [d.p.] <20) and a greater proportion of intermediate size chains (d.p. 30-90) than the native enzyme. High-performance anion-exchange chromatography (HPAEC) of the branching limited alpha-glucan product indicates that the truncated branching enzyme transfers a smaller proportion of chains with d.p. 4-11 and more chains longer than d.p. 12. Also, the genes encoding native or truncated branching enzyme were individually expressed in a branching enzyme-deficient mutant, AC71 (glgB(-)). By HPAEC analysis of the purified alpha-glucans we find that truncated branching enzyme transfers fewer chains of d.p. 5-11 and more chains longer than d.p. 12 relative to the full-length enzyme. These observations allow us to conclude that truncation of the amino-terminal domain has altered the branching pattern of the enzyme. Our results are consistent with the construction of hybrid branching enzymes from the maize isoforms.
Binderup
Kim
K
Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA.
Mikkelsen
René
R
Preiss
Jack
J
D015061:1,4-alpha-Glucan Branching Enzyme / Q000378:metabolism*; D000688:Amylose / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D010446:Peptide Fragments / Q000378:metabolism; D013379:Substrate Specificity
D010446:Peptide Fragments; D000688:Amylose; D015061:1,4-alpha-Glucan Branching Enzyme