   3.2.1.162 | metabolism |
the most important types of commercial carrageenans, namely kappa-, iota- and lambda-carrageenan, are esterified with one, two, and three sulfate groups per repeating disaccharide unit, being also called carrageenose 4'-sulfate, carrageenose 2,4'-disulfate, and carrageenose 2,6,2'-trisulfate, respectively. kappa-Carrageenans occur in the cell wall of some species of marine red algae, such as Chondrus sp., Gigartina sp., Eucheuma sp. and Iridaea sp. but is mostly extracted from tropical seaweed Euchema cottoni (also known as Kappaphycus alvarezii), while iota-carrageenans are mainly extracted from Eucheuma spinosum (also known as Eucheuma denticulatum). Because kappa- and iota-carrageenans are produced from my- and ny-carrageenans, respectively, during the extraction under alkaline at high temperatures or biosynthetically by a reaction catalyzed by the enzyme sulfohydrolase, these polysaccharides are often found in commercial samples. lambda-Carrageenans are extracted from red algae within the Gigartina and Chondrus genera, which produces this type of polysaccharide during the sporophytic stage. These algae are also a source of kappa- and iota-carrageenans when they are in the gametophytic stage, but because they produce mixed chain polysaccharide chains containing both kappa- and iota-units, extraction of kappa- and iota-carrageenans from the mentioned algae is preferred. Carrageenan classes based on the number and position of sulfate groups in the chain, overview. The sulfate and AD contents of commercial kappa-, iota-, and lambda-carrageenans have been determined by acid hydrolysis, infrared spectroscopy, and nuclear magnetic resonance (NMR) analyses and found to be, respectively, 25-30 and 28-35% for the kappa-type, 28-30 and 25-30% for iota-type and 32-39% and 0 for lambda-type, respectively |
755018 |
