A NOVEL ULVAN LYASE FAMILY WITH BROAD-SPECTRUM ACTIVITY FROM ULVAN UTILISATION LOCI OF FORMOSA AGARIPHILA KMM 3901

Conference poster, 2018

The rapid proliferation of members of green macroalgae in eutrophicated waters causes algal blooms. The biomass of these blooms, which is rich in polysaccharides, is underutilised and majorly left to decompose. Ulvan is one of such polysaccharides which constitutes up to 30 % of dry weight in Ulva
species. Ulvan and its oligosaccharides have potential applications in food and medicine. Ulvan lyases depolymerise ulvan via the β-elimination mechanism with the release of oligosaccharides that have unsaturated 4-deoxy-L-threo-hex-4-enopyranosiduronic acid at the non-reducing end. Ulvan
lyases belong to the PL24, PL25 or PL28 family in the CAZy database [2-5]. In this study, we identified and biochemically characterised a periplasmic novel broad-spectrum ulvan lyase from Formosa agariphila KMM 3901. The lyase was heterologously overexpressed in Escherichia coli, and purified
using a two-step purification. The purified recombinant enzyme depolymerised ulvan in an endolytic manner with a Km of 0.77 mg/ml. The enzyme was optimally active at 40 °C and pH 8.
This lyase also degraded heparan sulphate and chondroitin sulphate. Detailed analyses of the endproducts of the enzymatic endolytic depolymerisation of ulvan using 1H- and 13C-NMR and LC-MS revealed an unsaturated disaccharide (∆Rha3S) and a tetrasaccharide (∆Rha3S-Xyl-Rha3S) as the principal end-products. This ulvan lyase is a member of the polysaccharide utilisation loci for ulvan.
In contrast to the previously described ulvan lyases, this novel lyase is mostly composed of α-helices that form an (α/α)6 incomplete toroid domain and displays a remarkably broad-spectrum activity. This novel lyase is the first member of a new family, which sequence is not homologous to other ulvan
lyases.