Title: Effects of mutations on the insoluble glucan synthesized by Leuconostoc mesenteroides NRRL B-1118 glucansucrase Authors
Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2014
Publication Date: March 15, 2014
Citation: Cote, G.L., Skory, C.D. 2014. Effects of mutations at threonine-654 on the insoluble glucan synthesized by Leuconostoc mesenteroides NRRL B-1118 glucansucrase. Applied Microbiology and Biotechnology. DOI: 10.1007/s00253-014-5622-x. Interpretive Summary: In order to produce renewable polymers for a variety of applications, we have cloned an enzyme from a food-grade microbe and created several modified forms of the enzyme by replacing a single amino acid. The modified enzymes all produce water-insoluble polymers, but in varying yields and with different chemical and physical properties. The properties of the polymers suggest many uses, including several in foods, biomedical applications, and industrial films and fibers. By creating these modified enzymes, we demonstrate the feasibility of custom-tailoring the polymers for specific applications.
Technical Abstract: Twelve different amino acids were each substituted for Threonine-654 in a cloned glucansucrase from Leuconostoc mesenteroides NRRL B-1118 (DSR-I). The native enzyme produces a water-insoluble glucan containing approximately 44 mol% 1,3-disubstituted a-D-glucopyranosyl units and 29 mol% 1,6-disubstituted a-D-glucopyranosyl units. Several substitutions yielded an enzyme that produced an increased percentage of 1,3-disubstituted a-D-glucopyranosyl units, with corresponding decreases in 1,6-disubstituted a-D-glucopyranosyl units. Only one substitution, namely tyrosine, resulted in a significant increase in the percentage of 1,6-disubstituted a-D-glucopyranosyl units, with a concomitant increase in glucan yield. The mutated enzymes that produced the highest levels of 1,3-disubstituted a-D-glucopyranosyl units were also significantly activated by the addition of dextran, but glucan yields were also lower in these mutants.