Insights into alginate degradation through the characterization of a thermophilic exolytic alginate lyase.

Insights into alginate degradation through the characterization of a thermophilic exolytic alginate lyase. Appl Environ Microbiol. 2021 Jan 04;: Authors: Arntzen MØ, Pedersen B, Klau LJ, Stokke R, Oftebro M, Antonsen SG, Fredriksen L, Sletta H, Aarstad OA, Aachmann FL, Horn SJ, Eijsink VGH Abstract Enzymatic depolymerization of seaweed polysaccharides is gaining interest for the production of functional oligosaccharides and fermentable sugars. Herein, we describe a thermostable alginate lyase that belongs to Polysaccharide Lyase family 17 (PL17) and was derived from an Arctic Mid-Ocean Ridge (AMOR) metagenomics dataset. This enzyme, AMOR_PL17A, is a thermostable exolytic oligoalginate lyase (EC 4.2.2.26), which can degrade alginate, poly β-d-mannuronate and poly α-l-guluronate within a broad range of pH, temperature and salinity conditions. Site-directed mutagenesis showed that tyrosine Y251, previously suggested to act as catalytic acid, indeed is essential for catalysis; whereas mutation of tyrosine Y446, previously proposed to act as catalytic base, did not affect enzyme activity. The observed reaction products are protonated and deprotonated forms of the 4,5-unsaturated uronic acid monomer, Δ, two hydrates of DEH (4-deoxy-l-erythro-5-hexulosuronate), which are formed after ring opening and, finally, two epimers of a 5-membered hemiketal called 4-deoxy-d-manno-hexulofuranosidonate (DHF) formed through intramolecular cyclisatio...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research