Production of Structurally Defined Chito-Oligosaccharides with a Single N-Acetylation at Their Reducing End Using a Newly Discovered Chitinase from Paenibacillus pabuli

Partially acetylated chito-oligosaccharides (paCOSs) are bioactive compounds with potential medical applications. Their biological activities are largely dependent on their structural properties, in particular their degree of polymerization (DP) and the position of the acetyl groups along the glycan chain. The production of structurally defined paCOSs in a purified form is highly desirable to better understand the structure/bioactivity relationship of these oligosaccharides. Her; we describe a newly discovered chitinase from Paenibacillus pabuli (PpChi) and demonstrate by mass spectrometry that it essentially produces paCOSs with a DP of three and four that carry a single N-acetylation at their reducing end. We propose that this specific composition of glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) residues, as in GlcN((n)) GlcNAc(1), is due to a subsite specificity toward GIcN residues at the -2, -3, and -4 positions of the partially acetylated chitosan substrates. In addition, the enzyme is stable, as evidenced by its long shelf life, and active over a large temperature range, which is of high interest for potential use in industrial processes. It exhibits a k(cat) of 67.2 s(-1) on partially acetylated chitosan substrates. When PpChi was used in combination with a recently discovered fungal auxilary activity (AA11) oxidase, a sixfold increase in the release of oligosaccharides from the lobster shell was measured. PpChi represents an attractive biocatalyst for the green production of highly valuable paCOSs with a well-defined structure and the expansion of the relatively small library of chito-oligosaccharides currently available.

Automated summary

Partially acetylated chito-oligosaccharides (paCOSs) are bioactive compounds with potential medical applications, and their biological activities are largely dependent on their structural properties, especially the degree of polymerization (DP) and the position of acetyl groups. A newly discovered chitinase from Paenibacillus pabuli (PpChi) has been shown to produce structurally defined paCOSs with specific compositions, demonstrating stability and activity over a wide temperature range, making it a promising biocatalyst for industrial processes. When used in combination with a recently discovered fungal oxidase, PpChi significantly increases the release of oligosaccharides, contributing to the green production of valuable paCOSs with a well-defined structure.