title: Effects of mutations at threonine-654 on the insoluble glucan synthesized by Leuconostoc mesenteroides NRRL B-1118 glucansucrase.
abstract: Twelve different amino acids were each substituted for threonine-654 in a cloned glucansucrase from Leuconostoc mesenteroides NRRL B-1118. Both the native and the cloned enzyme with threonine at position 654 produced a water-insoluble glucan containing approximately 44 mol% 1,3-disubstituted α-D-glucopyranosyl units and 29 mol% 1,6-disubstituted α-D-glucopyranosyl units. Several substitutions yielded an enzyme that produced an increased percentage of 1,3-disubstituted α-D-glucopyranosyl units, with corresponding decreases in 1,6-disubstituted α-D-glucopyranosyl units. Only one substitution, tyrosine, resulted in a significant increase in the percentage of 1,6-disubstituted α-D-glucopyranosyl units, with a concomitant increase in glucan yield. The mutated enzymes that produced the highest levels of 1,3-disubstituted α-D-glucopyranosyl units were also significantly activated by the addition of dextran, but glucan yields were also lower in these mutants.
authors.affiliation: Renewable Product Technology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, 1815 North University St, Peoria, IL, 61604, USA, greg.cote@ars.usda.gov.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Côté
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Skory
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D005936:Glucans / Q000096:biosynthesis* / Q000737:chemistry; D016695:Glycosyltransferases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D007934:Leuconostoc / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D012995:Solubility; D013912:Threonine / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D013912:Threonine; D016695:Glycosyltransferases; C033837:alternansucrase