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- Title
Characterization of an α-agarase from <italic>Thalassomonas</italic> sp. LD5 and its hydrolysate.
- Authors
Zhang, Weibin; Xu, Jingnan; Liu, Dan; Liu, Huan; Lu, Xinzhi; Yu, Wengong
- Abstract
It has been a long time since the first α-agarase was discovered. However, only two α-agarases have been cloned and partially characterized so far and the study of α-agarases has lagged far behind that of β-agarases. Here, we report an α-agarase, AgaD, cloned from marine bacterium <italic>Thalassomonas</italic> sp. LD5. Its cDNA consists of 4401 bp, encoding a protein of 1466 amino acids. Based on amino acid similarity, AgaD is classified into glycoside hydrolase (GH) family GH96. The recombinant enzyme gave a molecular weight of about 180 kDa on SDS-PAGE and 360 kDa on Native-PAGE indicating it acted as a dimer. However, the recombinant enzyme is labile and easy to be fractured into series of small active fragments, of which the smallest one is about 70 kDa, matching the size of catalytic module. The enzyme has maximal activity at 35 °C and pH 7.4, and shows a strong dependence on the presence of calcium ions. AgaD degrades agarose to yield agarotetraose as the predominate end product. However, the hydrolysates are rapidly degraded to odd-numbered oligosaccharides under strong alkaline condition. The spectra of ESI-MS and 1H-NMR proved that the main hydrolysate agarotetraose is degraded into neoagarotriose, bearing the sequence of G-A-G (G, d-galactose; A, 3,6-anhydro-α-l-galactose). Unlike the alkaline condition, the hydrolysates are further hydrolyzed into smaller degree polymerization (DP) of agaro-oligosaccharides (AOS) in dilute strong acid. Therefore, this study provides more insights into the properties for both the α-agarases and the AOS.
- Subjects
AGARASE; AMINO acids; GLYCOSIDASES; OLIGOSACCHARIDES; ALKALINE solutions
- Publication
Applied Microbiology & Biotechnology, 2018, Vol 102, Issue 5, p2203
- ISSN
0175-7598
- Publication type
Article
- DOI
10.1007/s00253-018-8762-6