1 Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, Alberta T1J 4B1, Canada.
2 Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, Alberta T1J 4B1, Canada; Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta T1K 6T5, Canada.
3 Centre for Structural and Functional Genomics, Concordia University, Montreal, Quebec H4B 1R6, Canada.
4 Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 3P6, Canada.
5 School of Biology, Ridley Building 2, Newcastle University, Claremont Road, Newcastle upon Tyne NE1 7RU, United Kingdom.
6 Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta T1K 6T5, Canada.
7 Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, Alberta T1J 4B1, Canada; Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta T1K 6T5, Canada. Electronic address: wade.abbott@agr.gc.ca.

Discovery and characterization of family 39 glycoside hydrolases from rumen anaerobic fungi with polyspecific activity on rare arabinosyl substrates.

J Biol Chem. 2017 07 28;292(30):12606-12620

Authors: Jones DR, Uddin MS, Gruninger RJ, Pham TTM, Thomas D, Boraston AB, Briggs J, Pluvinage B, McAllister TA, Forster RJ, Tsang A, Selinger LB, Abbott DW

Abstract

Enzyme activities that improve digestion of recalcitrant plant cell wall polysaccharides may offer solutions for sustainable industries. To this end, anaerobic fungi in the rumen have been identified as a promising source of novel carbohydrate active enzymes (CAZymes) that modify plant cell wall polysaccharides and other complex glycans. Many CAZymes share insufficient sequence identity to characterized proteins from other microbial ecosystems to infer their function; thus presenting challenges to their identification. In this study, four rumen fungal genes (nf2152, nf2215, nf2523, and pr2455) were identified that encode family 39 glycoside hydrolases (GH39s), and have conserved structural features with GH51s. Two recombinant proteins, NF2152 and NF2523, were characterized using a variety of biochemical and structural techniques, and were determined to have distinct catalytic activities. NF2152 releases a single product, ß1,2-arabinobiose (Ara2) from sugar beet arabinan (SBA), and ß1,2-Ara2 and a-1,2-galactoarabinose (Gal-Ara) from rye arabinoxylan (RAX). NF2523 exclusively releases a-1,2-Gal-Ara from RAX, which represents the first description of a galacto-(a-1,2)-arabinosidase. Both ß-1,2-Ara2 and a-1,2-Gal-Ara are disaccharides not previously described within SBA and RAX. In this regard, the enzymes studied here may represent valuable new biocatalytic tools for investigating the structures of rare arabinosyl-containing glycans, and potentially for facilitating their modification in industrial applications.

PMID: 28588026 [PubMed - indexed for MEDLINE]