Alpha-1,4-glucan lyase, a new class of starch/glycogen degrading enzyme. I. Efficient purification and characterization from red seaweeds.

This study presents the first purification and characterization of an alpha-1,4-glucan lyase. The enzyme degraded alpha-1,4-glucan to produce 1,5-anhydrofructose. A simple and efficient purification procedure has been developed and the enzyme has been purified to homogeneity from two red seaweeds Gracilariopsis lemaneiformis and Gracilaria verrucosa. alpha-1,4-Glucan lyase was apparently a single polypeptide as a molecular weight of 111,000 was observed in SDS-gel electrophoresis, and 98,000 by gel filtration chromatography on Sephacryl S-200. Amino acid composition analysis of the enzyme showed high amounts of Asp/Asn, Gly and Glu/Gln. The isoelectric point of the enzyme was 3.9, as revealed by isoelectrofocusing. The concentrations of maltotriose, maltose and amylopectin that yield half of the maximum activity were 798 micrograms ml-1 (1.58 mM), 1,418 micrograms ml-1 (4.14 mM) and 1,600 micrograms ml-1, respectively. alpha-1,4-Glucan lyase exhibited a wide pH optimum range from pH 2.5 to 7.0 for maltose and from pH 3.5 to 7.5 for amylopectin. The optimal temperature for activity of the algal lyase was 50 degrees C when maltose or amylopectin was used as a substrate under the assay conditions. The Arrhenius activation energies were 45.8 and 44.0 kJ mol-1 for maltose and amylopectin as substrate, respectively. Only one form of alpha-1,4-glucan lyase was found in cell-free extracts of the two red seaweeds.