A Highly Denaturant-durable Alginate Lyase from a Marine Bacterium : Purification and Properties

Abstract

Poly(α-L-guluronate)lyase, which depolymerizes polyguluronate of alginate, was purified from the culture medium of a marine bacterium isolated from the intestine contents of a red sea bream, Pagrus major. The enzyme was homogeneous as judged by polyacrylamide gel electrophoresis in the presence and absence of SDS and the molecular weight of 42, 000 and 40, 000 on SDS gel electrophoresis and on a Sephacryl S200HR column chromatography, respectively. The activity of the enzyme was higher at around pH 8.5 and stable from pH 6-10. The active form of the enzyme, which has been thought to be once lost upon incubation of the enzyme at higher temperatures up to 80°C could be restored on cooling the enzyme. The residual activity was 45% even at 100°C. By treatment with other denaturants, the activity was maintained in 3% SDS and was 70% in 6M GHCl and 60% in 4M urea on incubation at 25°C for 30 min. In addition, several chemical reagents were tested for the relationship between the functional amino acid residue and the active form of the enzyme.