Degradation of lambda-carrageenan by Pseudoalteromonas carrageenovora lambda-carrageenase: a new family of glycoside hydrolases unrelated to kappa- and iota-carrageenases

Biochem J. 2007 May 15;404(1):105-14. doi: 10.1042/BJ20061359.

Abstract

Carrageenans are sulfated galactans found in the cell walls of red seaweeds. They are classified according to the number and the position of sulfate ester groups. lambda-Carrageenan is the most sulfated carrageenan and carries at least three sulfates per disaccharide unit. The sole known depolymerizing enzyme of lambda-carrageenan, the lambda-carrageenase from Pseudoalteromonas carrageenovora, has been purified, cloned and sequenced. Sequence analyses have revealed that the lambda-carrageenase, referred to as CglA, is the first member of a new family of GHs (glycoside hydrolases), which is unrelated to families GH16, that contains kappa-carrageenases, and GH82, that contains iota-carrageenases. This large enzyme (105 kDa) features a low-complexity region, suggesting the presence of a linker connecting at least two independent modules. The N-terminal region is predicted to fold as a beta-propeller. The main degradation products have been purified and characterized as neo-lambda-carratetraose [DP (degree of polymerization) 4] and neo-lambda-carrahexaose (DP6), indicating that CglA hydrolyses the beta-(1-->4) linkage of lambda-carrageenan. LC-MALLS (liquid chromatography-multi-angle laser light scattering) and (1)H-NMR monitoring of the enzymatic degradation of lambda-carrageenan indicate that CglA proceeds according to an endolytic mode of action and a mechanism of inversion of the anomeric configuration. Using 2-aminoacridone-labelled neo-lambda-carrabiose oligosaccharides, in the present study we demonstrate that the active site of CglA comprises at least 8 subsites (-4 to +4) and that a DP6 oligosaccharide binds in the subsites -4 to +2 and can be hydrolysed into DP4 and DP2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Carbohydrate Conformation
  • Carrageenan / chemistry
  • Carrageenan / isolation & purification
  • Carrageenan / metabolism*
  • Chromatography, Gel
  • Glycoside Hydrolases / chemistry
  • Glycoside Hydrolases / genetics*
  • Glycoside Hydrolases / metabolism*
  • Kinetics
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Oligosaccharides / chemistry
  • Oligosaccharides / metabolism
  • Open Reading Frames
  • Pseudoalteromonas / enzymology*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Substrate Specificity

Substances

  • Bacterial Proteins
  • Oligosaccharides
  • Recombinant Proteins
  • Carrageenan
  • Glycoside Hydrolases
  • lambda-carrageenase, Pseudoalteromonas

Associated data

  • GENBANK/AM397269