Characterization of glucosamine andN-acetylglucosamine oligomers by fast atom bombardment mass spectrometry

Sequence analysis of chitooligosaccharides by matrix-assisted laser desorption ionization postsource decay mass spectrometry

Chitin/chitosan oligosaccharides composed of 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-D-glucopyranose (GlcN) were prepared by chemical degradation of chitin or chitosan and separated by gel permeation chromatography. Oligosaccharides obtained after enzymatic hydrolysis of chitosan [F(A) 0.19] with a fungal chitinase were derivatized by reductive amination with 2-aminoacridone and sequenced by matrix-assisted laser desorption ionization time-of-flight postsource decay (PSD) mass spectrometry (MS). The sequence of a trimer, D1A2, was established as D-A-A. The composition of a hexamer D3A3 was ca. 65% D-A-D-D-A-A and 35% D-D-A-D-A-A. The PSD MS of a nonamer D5A4-amac revealed four isobaric species D-X-Y-D-X-Y-D-A-A, where A is GlcNAc, D is GlcN, and X and Y (X not equal Y) are mutually either D or A. This structure motif was also observed in a dodecamer D7A5 which was composed of eight isobaric sequences of the general formula (D-X-Y)(3)-D-A-A.

Chitin deacetylases: new, versatile tools in biotechnology

Chitin deacetylases have been identified in several fungi and insects. They catalyse the hydrolysis of N-acetamido bonds of chitin, converting it to chitosan. Chitosans, which are produced by a harsh thermochemical procedure, have several applications in areas such as biomedicine, food ingredients, cosmetics and pharmaceuticals. The use of chitin deacetylases for the conversion of chitin to chitosan, in contrast to the presently used chemical procedure, offers the possibility of a controlled, non-degradable process, resulting in the production of novel, well-defined chitosan oligomers and polymers.

Mode of action of chitin deacetylase from Mucor rouxii on N-acetylchitooligosaccharides

The mode of action of chitin deacetylase from the fungus Mucor rouxii on N-acetylchitooligosaccharides with a degree of polymerization 1-7 has been elucidated. Identification of the sequence of chitin oligomers following enzymatic deacetylation was verified by the alternative use of two specific exo-glycosidases in conjunction with HPLC. The results were further verified by 1H-NMR spectroscopy. It was observed that the length of the oligomer is important for enzyme action. The enzyme cannot effectively deacetylate chitin oligomers with a degree of polymerization lower than three. Tetra-N-acetylchitotetraose and penta-N-acetylchitopentaose are fully deacetylated by the enzyme, while in the case of tri-N-acetylchitotriose, hexa-N-acetylchitohexaose and hepta-N-acetylchitoheptaose the reducing-end residue always remains intact. Furthermore, the enzyme initially removes an acetyl group from the nonreducing-end residue of all chitin oligomers with a degree of polymerization higher than 2, and further catalyses the hydrolysis of the following acetamido groups in a processive fashion. The results are in agreement with the mode of action that the same enzyme exhibits on partially deacetylated water soluble chitosan polymers.

Comparison of the ability of partially N-acetylated chitosans and chitooligosaccharides to elicit resistance reactions in wheat leaves

Chitin, a linear polysaccharide composed of (1-->4)-linked 2-acetamido-2-deoxy-beta-D-glucopyranose (GlcNAc) residues, and chitosan, the fully or partially N-acetylated, water-soluble derivative of chitin composed of (1-->4)-linked GlcNAc and 2-amino-2-deoxy-beta-D-glucopyranose (GlcN), have been proposed as elicitors of defense reactions in higher plants. We tested and compared the ability of purified (1-->4)-linked oligomers of GlcNAc (tetramer to decamer) and of GlcN (pentamer and heptamer) and partially N-acetylated chitosans with degrees of acetylation (DA) of 1%, 15%, 35%, 49%, and 60% and average degrees of polymerization between 540 and 1100 to elicit phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, lignin deposition, and microscopically and macroscopically visible necroses when injected into the intercellular spaces of healthy, nonwounded wheat (Triticum aestivum L.) leaves. Purified oligomers of (1-->4)-linked GlcN were not active as elicitors, whereas purified oligomers of (1-->4)-linked GlcNAc with a degree of polymerization >/= 7 strongly elicited POD activities but not PAL activities. Partially N-acetylated, polymeric chitosans elicited both PAL and POD activities, and maximum elicitation was observed with chitosans of intermediate DAs. All chitosans but not the chitin oligomers induced the deposition of lignin, the appearance of necrotic cells exhibiting yellow autofluorescence under ultraviolet light, and macroscopically visible necroses; those with intermediate DAs were most active. These results suggest that different mechanisms are involved in the elicitation of POD activities by GlcNAc oligomers, and of PAL and POD activities by partially N-acetylated chitosan polymers and that both enzymes have to be activated for lignin biosynthesis and ensuing necrosis to occur.