Enzymatic depolymerization of alginate by two novel thermostable alginate lyases from Rhodothermus marinus

Justyna M. Dobruchowska, Bryndis Bjornsdottir, Olafur H. Fridjonsson, Josef Altenbuchner, Hildegard Watzlawick, Gerrit J. Gerwig, Lubbert Dijkhuizen, Johannis P. Kamerling, Gudmundur O. Hreggvidsson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Alginate (alginic acid) is a linear polysaccharide, wherein (1→4)-linked β-D-mannuronic acid and its C5 epimer, α-L-guluronic acid, are arranged in varying sequences. Alginate lyases catalyze the depolymerization of alginate, thereby cleaving the (1→4) glycosidic linkages between the monomers by a β-elimination mechanism, to yield unsaturated 4-deoxy-L-erythro-hex-4-enopyranosyluronic acid (Δ) at the non-reducing end of resulting oligosaccharides (α-L-erythro configuration) or, depending on the enzyme, the unsaturated monosaccharide itself. In solution, the released free unsaturated monomer product is further hydrated in a spontaneous (keto-enol tautomerization) process to form two cyclic stereoisomers. In this study, two alginate lyase genes, designated alyRm3 and alyRm4, from the marine thermophilic bacterium Rhodothermus marinus (strain MAT378), were cloned and expressed in Escherichia coli. The recombinant enzymes were characterized, and their substrate specificity and product structures determined. AlyRm3 (PL39) and AlyRm4 (PL17) are among the most thermophilic and thermostable alginate lyases described to date with temperature optimum of activity at ∼75 and 81°C, respectively. The pH optimum of activity of AlyRm3 is ∼5.5 and AlyRm4 at pH 6.5. Detailed NMR analysis of the incubation products demonstrated that AlyRm3 is an endolytic lyase, while AlyRm4 is an exolytic lyase, cleaving monomers from the non-reducing end of oligo/poly-alginates.

Original languageEnglish
Article number981602
Pages (from-to)981602
JournalFrontiers in Plant Science
Publication statusPublished - 20 Sep 2022

Bibliographical note

Funding Information:
This work was supported by EU FP7 grant 265992, AMYLOMICS; BBI grant MACROCASCADE 720755 and the BlueBio Cofund consortium grant, MARIKAT, Grant Icelandic Technology Development Fund 2011273-0611.

Publisher Copyright:
Copyright © 2022 Dobruchowska, Bjornsdottir, Fridjonsson, Altenbuchner, Watzlawick, Gerwig, Dijkhuizen, Kamerling and Hreggvidsson.

Other keywords

  • alginate oligosaccharides
  • guluronic acid
  • mannuronic acid
  • NMR spectroscopy
  • Rhodothermus marinus
  • thermophilic alginate lyase


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