Structure and function of a broad-specificity chitin deacetylase from Aspergillus nidulans FGSC A4

• Published in: Scientific reports Vol. 7; no. 1; pp. 1746 - 12
• Main Authors: Liu, Zhanliang, Gay, Laurie M., Tuveng, Tina R., Agger, Jane W., Westereng, Bjørge, Mathiesen, Geir, Horn, Svein J., Vaaje-Kolstad, Gustav, van Aalten, Daan M. F., Eijsink, Vincent G. H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11-05-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 631/45/607; 631/45/72/1205; 631/535/1266; 82/16; 82/80; 82/83; Acetic acid; Acetylation; Acetylglucosamine - metabolism; Amidohydrolases - chemistry; Amidohydrolases - metabolism; Amino Acid Sequence; Aspergillus nidulans; Aspergillus nidulans - enzymology; Bacterial Proteins - metabolism; Carrier Proteins - metabolism; Cell walls; Chitin; Chitin - chemistry; Chitin - metabolism; Chitin deacetylase; Chitosan; Crystal structure; Deacetylation; Enzymes; Fungi; Humanities and Social Sciences; Intracellular Signaling Peptides and Proteins; Kinetics; Mass spectrometry; Mass spectroscopy; Models, Molecular; Monooxygenase; multidisciplinary; N-Acetylglucosamine; Peptidoglycans; Polymers; Science; Science (multidisciplinary); Sequence Alignment; Solubility; Static Electricity; Structure-Activity Relationship; Structure-function relationships; Substrate Specificity; Sugar; Waste streams; Xylans - metabolism
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-02043-1

Enzymatic conversion of chitin, a β-1,4 linked polymer of
N
-acetylglucosamine, is of major interest in areas varying from the biorefining of chitin-rich waste streams to understanding how medically relevant fungi remodel their chitin-containing cell walls. Although numerous chitinolytic enzymes have been studied in detail, relatively little is known about enzymes capable of deacetylating chitin. We describe the structural and functional characterization of a 237 residue deacetylase (
An
CDA) from
Aspergillus nidulans
FGSC A4.
An
CDA acts on chito-oligomers, crystalline chitin, chitosan, and acetylxylan, but not on peptidoglycan. The
K
m
and
k
cat
of
An
CDA for the first deacetylation of penta-
N
-acetyl-chitopentaose are 72 µM and 1.4 s
−1
, respectively. Combining mass spectrometry and analyses of acetate release, it was shown that
An
CDA catalyses mono-deacetylation of (GlcNAc)
2
and full deacetylation of (GlcNAc)
3–6
in a non-processive manner. Deacetylation of the reducing end sugar was much slower than deacetylation of the other sugars in chito-oligomers. These enzymatic characteristics are discussed in the light of the crystal structure of
An
CDA, providing insight into how the chitin deacetylase may interact with its substrates. Interestingly,
An
CDA activity on crystalline chitin was enhanced by a lytic polysaccharide monooxygenase that increases substrate accessibility by oxidative cleavage of the chitin chains.