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Biochemical characterization of a novel cold-adapted GH39 [beta]-agarase, AgaJ9, from an agar-degrading marine bacterium Gayadomonas joobiniege G7
Ist Teil von
Applied microbiology and biotechnology, 2017-03, Vol.101 (5), p.1965
Ort / Verlag
Heidelberg: Springer
Erscheinungsjahr
2017
Link zum Volltext
Quelle
SpringerLink Journals
Beschreibungen/Notizen
Gayadomonas joobiniege G7 is an agar-degrading marine bacterium belonging to a novel genus. Genomic sequencing of G. joobiniege revealed that AgaJ9 (formerly YjdB) belonging to the glycoside hydrolase (GH) 39 family. It showed the highest similarity (47% identity) to a putative [beta]-agarase from Catenovulum agarivorans DS-2, an agar-degrading marine bacterium sharing the highest similarity in the nucleotide sequence of 16s rRNA gene with G. joobiniege G7. The agaJ9 gene encodes a protein (134 kDa) of 1205 amino acids, including a 23-amino acid signal peptide. The agarase activity of purified AgaJ9 was confirmed by zymogram analysis. The optimum pH and temperature for AgaJ9 activity were determined as 5 and 25 °C, respectively. Notably, AgaJ9 is a cold-adapted [beta]-agarase retaining more than 80% of its activity even at a temperature of 5 °C. In addition, gel filtration chromatography revealed that AgaJ9 exists as two forms, dimer and monomer. Although the two forms had similar enzymatic properties, their kinetic parameters were different. The K.sub.m and V.sub.max of dimeric AgaJ9 for agarose was 0.68 mg/ml (5.7 x 10.sup.-6 M) and 17.2 U/mg, respectively, whereas the monomeric form had a K.sub.m of 1.43 mg/ml (1.2 x 10.sup.-5 M) and V.sub.max of 10.7 U/mg. Thin-layer chromatography and agarose-liquefying analyses revealed that AgaJ9 is an endo-type [beta]-agarase that hydrolyzes agarose into neoagarotetraose and neoagarobiose. This study is the first report of a GH39 [beta]-agarase with a cold-adapted enzymatic feature, a unique attribute, which may be useful for industrial applications.