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bioRxiv · 10.1101/2023.07.28.550916

Genetic and functional diversity of beta-N-acetylgalactosamine residue-targeting glycosidases expanded by deep-sea metagenome

Sumida, T.·Hiraoka, S.·Usui, K.·Ishiwata, A.·Sengoku, T.·Stubbs, K. A.·Tanaka, K.·Deguchi, S.·Fushinobu, S.·Nunoura, T.
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Abstract

{beta}-N-Acetylgalactosamine-containing glycans play essential roles in several biological processes, including cell adhesion, signal transduction, and immune responses. {beta}-N-Acetylgalactosaminidases hydrolyze {beta}-N-acetylgalactosamine linkages of various glycoconjugates. However, their biological significance remains ambiguous, primarily because only one type of enzyme, exo-{beta}-N-acetylgalactosaminidases that specifically act on {beta}-N-acetylgalactosamine residues, has been documented so far. In this study, we identified three novel glycoside hydrolase families distributed among all three domains of life and characterized eight novel {beta}-N-acetylgalactosaminidases and {beta}-N-acetylhexosaminidase through sequence-based screening of deep-sea metagenomes and subsequent searching of public protein databases. Despite low sequence similarity, the crystal structures of these enzymes demonstrate that all enzymes share a prototype structure and diversify their substrate specificities (endo-, dual-endo/exo-, and exo-) through the accumulation of mutations and insertional amino acid sequences. The diverse {beta}-N-acetylgalactosaminidases reported in this study could facilitate the comprehension of their structures and functions and present novel evolutionary pathways for expanding their substrate specificity.

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Sumida, T., Hiraoka, S., Usui, K., Ishiwata, A., Sengoku, T., Stubbs, K. A., Tanaka, K., Deguchi, S., Fushinobu, S., Nunoura, T.. 2023-07-28. Genetic and functional diversity of beta-N-acetylgalactosamine residue-targeting glycosidases expanded by deep-sea metagenome. https://doi.org/10.1101/2023.07.28.550916

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