title: Characterization of a glucosamine/glucosaminide N-acetyltransferase of Clostridium acetobutylicum.
abstract: Many bacteria, in particular Gram-positive bacteria, contain high proportions of non-N-acetylated amino sugars, i.e., glucosamine (GlcN) and/or muramic acid, in the peptidoglycan of their cell wall, thereby acquiring resistance to lysozyme. However, muramidases with specificity for non-N-acetylated peptidoglycan have been characterized as part of autolytic systems such as of Clostridium acetobutylicum. We aim to elucidate the recovery pathway for non-N-acetylated peptidoglycan fragments and present here the identification and characterization of an acetyltransferase of novel specificity from C. acetobutylicum, named GlmA (for glucosamine/glucosaminide N-acetyltransferase). The enzyme catalyzes the specific transfer of an acetyl group from acetyl coenzyme A to the primary amino group of GlcN, thereby generating N-acetylglucosamine. GlmA is also able to N-acetylate GlcN residues at the nonreducing end of glycosides such as (partially) non-N-acetylated peptidoglycan fragments and β-1,4-glycosidically linked chitosan oligomers. Km values of 114, 64, and 39 μM were determined for GlcN, (GlcN)2, and (GlcN)3, respectively, and a 3- to 4-fold higher catalytic efficiency was determined for the di- and trisaccharides. GlmA is the first cloned and biochemically characterized glucosamine/glucosaminide N-acetyltransferase and a member of the large GCN5-related N-acetyltransferases (GNAT) superfamily of acetyltransferases. We suggest that GlmA is required for the recovery of non-N-acetylated muropeptides during cell wall rescue in C. acetobutylicum.
authors.affiliation: Fachbereich Biologie, Molekulare Mikrobiologie, Universität Konstanz, Constance, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Reith
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayer
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000201:enzymology*; D004795:Enzyme Stability; D005944:Glucosamine / Q000378:metabolism; D007700:Kinetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D000105:Acetyl Coenzyme A; D000123:Acetyltransferases; C020580:glucosamine acetyltransferase; D005944:Glucosamine