Porphyran is a sulfated

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...

derived from red algae of the genus ''

Porphyra ''Porphyra'' is a genus of coldwater seaweeds that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.Brodie, J.A. and Irvine, ...

''.

Composition

Porphyran is a complex sulfated

. It is a highly substituted complex carbohydrate related to

agarose Agarose is a heteropolysaccharide, generally extracted from certain red seaweed. It is a linear polymer made up of the repeating unit of agarobiose, which is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose. Agarose is ...

with a linear backbone consisting of 3- linked beta-D- galactosyl units alternating with either 4-linked alpha-L-galactosyl 6-sulfate or 3,6-anhydro-alpha-L-galactosyl units. The composition includes 6-O-sulfated L-

galactose Galactose (, '' galacto-'' + ''-ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecu ...

, 6-O-

methylated In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These ...

D-galactose, L-galactose, 3,6-anhydro-L-galactose, 6-O-methyl D-galactose and

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

sulfate. Some of the ester is present as 1-4-linked L-galactose 6-sulfate. The precise composition of porphyran shows

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and ...

al and

environmental A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...

variations. In ''Porphyra haitanensis'', the L-residues are mainly composed of alpha-L-galactosyl 6-sulfate units, and the 3,6-anhydro-galactosyl units are minor. In ''Porphyra capensis'', the ratio of alpha-L-galactose-6-sulfate and the 3,6-anhydrogalactose is 1.2:1. Porphyran is converted to agarose by cyclization of L-galactose-6-sulfate to 3,6-anhydro-L-galactose.

References

{{Reflist Polysaccharides

Composition

See also

References