Agaropectin is one of the two main components of
agar
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from " ogonori" and " tengusa". As found in nature, agar is a mixture of two components, t ...
.
Structure
Agaropectin is a sulfated
galactan mixture which composes agar by 30% composition. It is composed of varying percentages of
organosulfate
In organosulfur chemistry, organosulfates are a class of organic compounds sharing a common functional group with the structure . The core is a sulfate group and the R group is any organic residue. All organosulfates are formally esters deri ...
s (sulfate esters),
D-glucuronic acid and small amounts of
pyruvic acid
Pyruvic acid (CH3COCOOH) is the simplest of the keto acids, alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate acid, conjugate base, CH3COCOO−, is an metabolic intermediate, intermediate in several m ...
. It is made up of alternating units of
D-galactose and
L-galactose heavily modified with acidic side-groups which are usually
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
,
glucuronate, and
pyruvate
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic ...
.
Pyruvic acid is possibly attached in an acetal form to the
D-galactose residues of the agarobiose skeleton. The sulfate content of the agar depends on the source of the raw material from which it is derived.
Acetylation
:
In chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed ''acetate esters'' or simply ''acetates''. Deacetylation is the opposite react ...
of agaropectin yields the chloroform-insoluble agaropectin acetate, as opposed to agarose acetate. This process can be used to separate the two polysaccharides via
fractionation
Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which t ...
.
Use
Agaropectin has no commercial value and is discarded during the commercial processing of agar, and food grade agar is mainly composed of agarose with a molecular weight of about 120 kDa.
References
{{Reflist
Polysaccharides
Organosulfates