Physical state of kappa-carrageenan modulates the mode of action of kappa-carrageenase from Pseudoalteromonas carrageenovora.
Pseudoalteromonas carrageenovora kappa-carrageenase is a glycoside hydrolase involved in the bioconversion of carrageenans. Carrageenans are sulfated galactans that are densely packed in red algal cell walls. Previous crystallographic investigations revealed that the active site of kappa-carrageenase has a tunnel-shaped topology, suggesting a processive mode of action for this enzyme. To biochemically characterize the enzymatic depolymerization of kappa-carrageenan, soluble and solid substrates (in both gel and powder forms) were incubated with P. carrageenovora kappa-carrageenase. The average molecular mass of soluble carrageenan decreased rapidly, and all possible degradation products were observed, suggesting random degradation of kappa-carrageenan. In contrast, as expected for a processive-type carrageenase, the average molecular mass of solid carrageenan decreased very slowly, and tetrasaccharide production was high. Interestingly, experimentally determined processivity was similar for gel and powder, suggesting that, in addition to an adapted catalytic site, the substrate must be in the solid state for kappa-carrageenase processivity to operate, whatever the level of carrageenan ordering.
Lemoine
Maud
M
Université Pierre et Marie Curie, Paris VI, CNRS, Marine Plants and Biomolecules, UMR 7139, Station Biologique, Roscoff Cedex, France.
Nyvall Collén
Pi
P
Helbert
William
W
D001426:Bacterial Proteins / Q000378:metabolism*; D002351:Carrageenan / Q000737:chemistry* / Q000648:ultrastructure; D002850:Chromatography, Gel; D004586:Electrophoresis; D005782:Gels; D006026:Glycoside Hydrolases / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D031161:Pseudoalteromonas / Q000187:drug effects / Q000201:enzymology*; D012995:Solubility / Q000187:drug effects
D001426:Bacterial Proteins; D005782:Gels; D009844:Oligosaccharides; D011189:Potassium Chloride; D002351:Carrageenan; D006026:Glycoside Hydrolases; C019846:kappa-carrageenase protein, Alteromonadaceae