Abstract
N, N′, N″-Tri(monochloro)acetylchitotriose prepared by N-monochloroacetylation of chitotriose trihydrochloride was successfully polymerized into higher-molecular-weight oligomers by a lysozyme-catalyzed transglycosylation reaction, and a following base-catalyzed N-demonochloroacetylation gave a chitosan oligomer mixture mainly composed of oligomers with dp >6. Partially N-deacetylated chitin oligomers (DAC oligomers) with dp 4–12 were synthesized by the enzyme reaction using N, N′, N″-tri(monochloro)acetylchitotriose and N, N′, N″-triacetylchitotriose (chitin trimer) as initial substrates followed by N-demonochloroacetylation. The structures of synthetic oligomers were analyzed by 1H NMR spectroscopy, enzymatic hydrolysis and nitrous acid deamination-NaBH 4 reduction treatment. The dp of synthetic oligomers was measured by MALDI TOF MS (matrix-assisted laser desorption ionization time-of-flight mass spectrometry) using per- N-acetylated derivatives. The synthetic chitosan and DAC oligomers were strong elicitors for phytoalexin induction in Pisum sativum and Phaseolus vulgaris. This chemo-enzymatic method utilizing N-acylated chitotrioses as substrates is a novel approach to the synthesis of high-molecular-weight chitosan oligomers and DAC oligomers of biological importance.
Published Version
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