Characterization and overexpression of a glycosyl hydrolase family 16 beta-agarase YM01-1 from marine bacterium Catenovulum agarivorans YM01T

Agar, usually extracted from seaweed, has a wide variety of industrial applications due to its gelling and stabilizing characteristics. Agarases are the enzymes which hydrolyze agar into agar oligosaccharides. The produced agar oligosaccharides have been widely used in cosmetic, food, and medical fields due to their biological functions. A beta-agarase gene, YM01-1, was cloned and expressed from a marine bacterium Catenovulum agarivorans YM01T. The encoding agarase of YM01-1 consisted of 331 amino acids with an apparent molecular mass of 37.7 kDa and a 23-amino-acids signal peptide. YM01-1 belongs to glycoside hydrolase 16 (GH16) family based on the amino acid sequence homology. The optimum pH and temperature for its activity was 7.0 and 50 °C, respectively. YM01-1 was stable at a pH of pH 6.0-9.0 and temperatures below 45 °C. Thin layer chromatography (TLC) and ion trap mass spectrometer of the YM01-1 hydrolysis products displayed that YM01-1 was an endo-type β-agarase and degrades agarose, neoagarohexaose, neoagarotetraose into neoagarobiose. The Km, Vmax, Kcat and Kcat/Km values of the YM01-1 for agarose were 8.69 mg/ml, 4.35 × 103 U/mg, 2.4 × 103 s−1 and 2.7 × 106 s−1 M−1, respectively. Hence, the enzyme with high agarolytic activity and single end product was different from other GH16 agarases, which has potential applications for the production of oligosaccharides with remarkable activities.