Characterization of Mannuronan C-5-Epimerase Genes from the Brown Alga Laminaria digitata

• Published in: Plant physiology (Bethesda) Vol. 133; no. 2; pp. 726 - 735
• Main Authors: Nyvall, Pi, Erwan Corre, Claire Boisset, Tristan Barbeyron, Sylvie Rousvoal, Delphine Scornet, Kloareg, Bernard, Catherine Boyen
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.10.2003; American Society of Plant Physiologists
• Subjects: Agronomy. Soil science and plant productions; Algae; Alginates; Amino Acid Sequence; Bacteria; Biological and medical sciences; Carbohydrate Epimerases - chemistry; Carbohydrate Epimerases - classification; Carbohydrate Epimerases - genetics; Cell walls; Classical and quantitative genetics. Population genetics. Molecular genetics; Cloning, Molecular; Complementary DNA; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; Generalities. Genetics. Plant material; Genes, Plant; Genes. Genome; Genetics and breeding of economic plants; Genetics, Genomics, and Molecular Evolution; Laminaria - classification; Laminaria - enzymology; Laminaria - genetics; Laminaria digitata; mannuronan C-5-epimerase; Marine; Models, Molecular; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Multigene Family; Open reading frames; Phaeophyceae; Phylogeny; Plants; Protein Conformation; Protoplasts; Protoplasts - enzymology; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Sequence Homology, Amino Acid; Sporophytes; Viruses; Algae; Phylogenetic tree; Biological evolution; Marine plant; Biosynthesis; Metabolic pathway; Alginates; Gene expression; Characterization; Heterokontophyta; Gene; Bacteria; Molecular cloning; Laminaria digitata; Comparative study; Phaeophyceae; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.103.025981

Alginate is an industrially important polysaccharide obtained commercially by harvesting brown algae. The final step in alginate biosynthesis, the epimerization of β-1,4-D-mannuronic acid to α-1,4-L-guluronic acid, a structural change that controls the physicochemical properties of the alginate, is catalyzed by the enzyme mannuronan C-5-epimerase. Six different cDNAs with homology to bacterial mannuronan C-5-epimerases were isolated from the brown alga Laminaria digitata (Phaeophyceae). Hydrophobic cluster analysis indicated that the proteins encoded by the L. digitata sequences have important structural similarities to the bacterial mannuronan C-5-epimerases, including conservation of the catalytic site. The expression of the C-5-epimerase genes was examined by northern-blot analysis and reverse transcriptase-polymerase chain reaction in L. digitata throughout a year. Expression was also monitored in protoplast cultures by northern and western blot, reverse transcriptase-polymerase chain reaction, and activity measurements. From both the structural comparisons and the expression pattern, it appears that the cDNAs isolated from L. digitata encode functional mannuronan C-5-epimerases. The phylogenetic relationships of the bacterial and brown algal enzymes and the inferences on the origin of alginate biosynthetic machinery are discussed.