Specificity of a β-porphyranase produced by the carrageenophyte red alga Chondrus crispus and implications of this unexpected activity on red algal biology - INRAE - Institut national de recherche pour l’agriculture, l’alimentation et l’environnement Accéder directement au contenu
Article Dans Une Revue Journal of Biological Chemistry Année : 2022

Specificity of a β-porphyranase produced by the carrageenophyte red alga Chondrus crispus and implications of this unexpected activity on red algal biology

Résumé

The carrageenophyte red alga Chondrus crispus produces three family 16 glycoside hydrolases (CcGH16-1, -2 and -3). Phylogenetically, the red algal GH16 members are closely related to bacterial GH16 homologues from subfamilies 13 and 14, which have characterized marine bacterial β-carrageenase and β-porphyranase activities, respectively, yet the functions of these CcGH16 hydrolases have not been determined. Here, we first confirmed the gene locus of the ccgh16-3 gene in the alga to facilitate further investigation. Next, our biochemical characterization of CcGH16-3 revealed an unexpected β-porphyranase activity, since porphyran is not a known component of the C. crispus extracellular matrix. Kinetic characterization was undertaken on natural porphyran substrate with an experimentally determined molecular weight. We found CcGH16-3 has a pH optimum between 7.5-8.0; however, it exhibits reasonably stable activity over a large pH range (pH 7.0-9.0). CcGH16-3 has a KM of 4.0 ± 0.8 μM, a kcat of 79.9 ± 6.9 s-1 and a kcat/KM of 20.1 ± 1.7 μM-1.s-1. We structurally examined fine enzymatic specificity by performing a subsite dissection. CcGH16-3 has a strict requirement for D-galactose and L-galactose-6-sulfate in its -1 and +1 subsites, respectively, whereas the outer subsites are less restrictive. CcGH16-3 is one of a handful of algal enzymes characterized with a specificity for a polysaccharide unknown to be found in their own extracellular matrix. This β-porphyranase activity in a carrageenophyte red alga may provide defense against red algal pathogens or, alternatively, provide a competitive advantage in niche colonization.

Dates et versions

hal-03894158 , version 1 (12-12-2022)

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Copyright (Tous droits réservés)

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G. Manat, M. Fanuel, D. Jouanneau, M. Jam, J. Mac-Bear, et al.. Specificity of a β-porphyranase produced by the carrageenophyte red alga Chondrus crispus and implications of this unexpected activity on red algal biology. Journal of Biological Chemistry, 2022, 298 (12), pp.102707. ⟨10.1016/j.jbc.2022.102707⟩. ⟨hal-03894158⟩
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