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The molecular basis of endolytic activity of a multidomain alginate lyase from Defluviitalea phaphyphila, a representative of a new lyase family, PL39

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Author(s)

  • Shiqi Ji
  • Samuel R Dix
  • Adli A Aziz
  • Svetlana E Sedelnikova
  • Patrick J Baker
  • John B Rafferty
  • Per A Bullough
  • Svetomir B Tzokov
  • Jon Agirre
  • Fu-Li Li
  • David W Rice

Department/unit(s)

Publication details

JournalThe Journal of biological chemistry
DateAccepted/In press - 17 Oct 2019
DateE-pub ahead of print - 17 Oct 2019
DatePublished (current) - 29 Nov 2019
Issue number48
Volume294
Number of pages15
Pages (from-to)18077-18091
Early online date17/10/19
Original languageEnglish

Abstract

Alginate is a polymer containing two uronic acid epimers, β-d-mannuronate (M) and α-l-guluronate (G), and is a major component of brown seaweed that is depolymerized by alginate lyases. These enzymes have diverse specificity, cleaving the chain with endo- or exotype activity and with differential selectivity for the sequence of M or G at the cleavage site. Dp0100 is a 201-kDa multi-modular, broad-specificity endotype alginate lyase from the marine thermophile Defluviitalea phaphyphila, which uses brown algae as a carbon source, converting it to ethanol, and bioinformatics analysis suggested that its catalytic domain represents a new polysaccharide lyase family, PLxx. The structure of the Dp0100 catalytic domain, determined at 2.07 Å resolution, revealed that it comprises three regions strongly resembling those of the exotype lyase families PL15 and PL17. The conservation of key catalytic histidine and tyrosine residues belonging to the latter suggest these enzymes share mechanistic similarities. A complex of Dp0100 with a pentasaccharide, M5, showed that the oligosaccharide is located in subsites -2, -1, +1, +2, and +3 in a long, deep canyon open at both ends, explaining the endotype activity of this lyase. This contrasted with the hindered binding sites of the exotype enzymes, which are blocked such that only one sugar moiety can be accommodated at the -1 position in the catalytic site. The biochemical and structural analyses of Dp0100, the first for this new class of endotype alginate lyases, has furthered our understanding of the structure-function and evolutionary relationships within this important class of enzymes.

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© 2019 American Society for Biochemistry and Molecular Biology. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

    Research areas

  • alginate lyase, carbohydrate-binding protein, crystal structure, metalloenzyme, oligosaccharide, structure–function, substrate specificity

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