Efficient preparation and production of ulvan oligosaccharides by using a new PL25 family ulvan lyase from Alteromonas sp. 76–1

Ulvan lyase is a useful tool which can degrade ulvan into oligosaccharides with a range of biological activities. In this study, the ulvan lyase ULA-3 from Alteromonas sp. 76–1, which was a 1467-bp encoded 489-amino acid residue protein, has been cloned, heterologously expressed and biochemically characterized. ULA-3 showed the maximum activity at 45 ˚C and pH 9.0. The K_m is 1.879 mg mL⁻¹ and V_max is 2.597 µmol min⁻¹ mL⁻¹. Its enzyme activity was outstanding at 11.754 U mg⁻¹. Moreover, its metal ion stability is exceptionally good and most metal ions at a concentration of 1 mM have no inhibitory effect on its activity. It can endolytically degrade ulvan into oligosaccharides with a degree of polymerization (Dp) of 2–4 and with unsaturated double bond through the β-elimination reaction, which mainly cleaves the glycosidic bond between rhamnose and uronic acids. All in all, our study has increased the ulvan lyase database and offers the opportunity to fully utilize ulvan, a green biomass resource from marine algae.