Affiliation:
1. Fachbereich Biologie, Molekulare Mikrobiologie, Universität Konstanz, 78457 Constance, Germany
Abstract
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
gl
ucosa
m
ine/glucosaminide
N
-
a
cetyltransferase). 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.
K
m
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
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
26 articles.
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