Identification and characterization of a thermostable endolytic β-agarase Aga2 from a newly isolated marine agarolytic bacteria Cellulophaga omnivescoria W5C

Kristine Rose M. Ramos, Kris Niño G. Valdehuesa, Grace M. Nisola, Won Keun Lee, Wook Jin Chung

Research output: Contribution to journalArticlepeer-review

Abstract

Research on the enzymatic breakdown of seaweed-derived agar has recently gained attention due to the progress in green technologies for marine biomass utilization. The enzymes known as agarases catalyze the cleavage of glycosidic bonds within the polysaccharide. In this study, a new β-agarase, Aga2, was identified from Cellulophaga omnivescoria W5C. Aga2 is one of four putative agarases from the W5C genome, and it belongs to the glycoside hydrolase 16 family. It was shown to be exclusive to the Cellulophaga genus. Agarase activity assays showed that Aga2 is an endolytic-type β-agarase that produces tetrameric and hexameric neoagaro-oligosaccharides, with optimum activity at 45 °C and pH 8.0. Zinc ions slightly enhanced its activity while manganese ions had inhibitory effects even at very low concentrations. Aga2 has a Km of 2.59 mg mL−1 and Vmax of 275.48 U mg−1. The Kcat is 1.73 × 102 s−1, while the Kcat/Km is 8.04 × 106 s−1 M−1. Aga2 also showed good thermostability at 45 °C and above, and retained >90% of its activity after repeated freeze-thaw cycles. Bioinformatic analysis of its amino acid sequence revealed that intrinsic properties of the protein (e.g. presence of certain dipeptides and the relative volume occupied by aliphatic amino acids) and tertiary structural elements (e.g. presence of salt bridges, hydrophobic interactions and H-bonding) contributed to its thermostability.

Original languageEnglish
Pages (from-to)261-267
Number of pages7
JournalNew Biotechnology
Volume40
Early online date27 Sept 2017
DOIs
Publication statusPublished - 25 Jan 2018
Externally publishedYes

Keywords

  • Aga2
  • Cellulophaga omnivescoria
  • Neoagarohexaose
  • Neoagarotetraose
  • β-Agarase

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