An agarase of glycoside hydrolase family 16 from marine bacterium Aquimarina agarilytica ZC1

Abstract

A novel β-agarase gene aga672 was cloned from strain ZC1, the typical strain of agar-degrading Aquimarina agarilytica. Gene aga672 is composed of 2130 bp, and the encoded protein Aga672 showed an amino acid sequence identity of only 42% with reported agarases. Aga672 should belong to glycoside hydrolase family 16 according to the protein sequence similarity. The molecular mass of the recombinant Aga672 was estimated to be 98 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Aga672 decomposed agarose to produce neoagarotetraose, neoagarohexaose and neoagarooctaose as the main products. That is the main difference between Aga672 and other reported agarases of family GH16. The Km and Vmax for agarose degradation were 59.8 mg mL-1 and 154.3 U mg-1, respectively. The activity of Aga672 was stable at temperatures below 40°C and at pH 7.0-11.0 with the maximal agarase activity at 25°C and pH 7.0. The results showed that agarase Aga672 could be suitable to hydrolyze the gelated agarose. Thus, it has potential applications in the production of neoagarooligosaccharides directly from red alga.