Polysaccharide - English spelling: polysaccharide

Japanese: 多糖 - たとう（英語表記）polysaccharide

A general term for carbohydrates formed by dehydration of 10 or more monosaccharides. Also called glycan or polyglycose. Among carbohydrates, sugars that cannot be hydrolyzed to simpler compounds are called monosaccharides. Usually, sugars consisting of 2 to 10 monosaccharides are called oligosaccharides (also called oligosaccharides), and sugars consisting of more than 10 monosaccharides are called polysaccharides, but the distinction between the two is not clear.

[Tokuhisa Sachiko]

Polysaccharide Classification

Polysaccharides are classified from various viewpoints. Those composed of the same monosaccharides are called simple polysaccharides (also called homopolysaccharides or homoglycans), and those composed of different monosaccharides are called complex polysaccharides (also called heteropolysaccharides or heteroglycans). Polysaccharides that contain a lot of uronic acid (compounds in which the _-CH2OH at the end of aldose is oxidized to a carboxyl group -COOH) or ester sulfate (compounds _in which sulfate _H2SO4 is dehydrated to the hydroxyl group -OH of a sugar) are called acidic polysaccharides. Polysaccharides that contain only neutral sugars are called neutral polysaccharides. Homopolysaccharides whose constituent sugars are pentose (also called five-carbon sugar) and hexose (also called six-carbon sugar) are called pentosans and hexosans, respectively. A group of polysaccharides whose constituent sugars are uronic acid and amino sugars (compounds in which the hydroxyl group -OH of a sugar is replaced with an amino group _-NH2 ) are called mucopolysaccharides (also called glycosaminoglycans). Polysaccharides bound to lipids are classified as glycolipids (glyceroglycolipids, sphingoglycolipids, etc.). Depending on their function, they are also called storage polysaccharides (starch, etc.), structural polysaccharides (cellulose, etc.), and functional polysaccharides (heparin, etc.).

[Tokuhisa Sachiko]

Polysaccharide Name

The suffix "-ose" of the constituent sugar is changed to "-an." For example, a homopolysaccharide whose constituent sugar is glucose is called a glucan. Heteropolysaccharides are made by arranging the constituent monosaccharides in alphabetical order and adding the glycan, for example, galactomannoglycan. Many are called by common names such as inulin and pectin.

[Tokuhisa Sachiko]

Properties of polysaccharides

Polysaccharides are polymeric substances that compose living organisms, and are found most abundantly in nature along with proteins and lipids. They are generally amorphous solids, have various degrees of solubility in water, are not sweet, and do not reduce Fehling's solution (a reagent used to detect and quantify reducing sugars). Polysaccharides are decomposed into oligosaccharides by acids and enzymes. There are enzymes specific to each polysaccharide. For example, starch, glycogen, and cellulose are decomposed by amylase, glycogen phosphorylase, and cellulase, respectively. Polysaccharides are detected by oxidizing hydroxyl groups with periodic acid and coloring the resulting aldehyde groups with Schiff's reagent. Polysaccharides are used in a wide range of industrial applications, including papermaking, textiles, plastics, food, and medicine.

[Tokuhisa Sachiko]

"Polysaccharide Biochemistry," supervised by Egami Fujio and edited by Suzuki Osamu et al. (1969, Kyoritsu Publishing)" ▽ "Biochemistry Data Book," edited by the Japanese Biochemical Society (1979, abridged edition 1981, Tokyo Kagaku Dojin)" ▽ "Methods for Separation and Purification of Polysaccharides," edited by Matsuda Kazuo (1987, Academic Press Center)" ▽ "Structure and Biological Activity of Polysaccharides," edited by Miyazaki Toshio (1990, Asakura Publishing)" ▽ "Plant Cell Walls and Polysaccharides," written by Sakurai Naoki, Yamamoto Ryoichi, and Kato Yoji (1991, Baifukan Publishing)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

単糖類が10個以上脱水結合して生じた糖質の総称。グリカンglycan、ポリグリコースpolyglycoseともいう。炭水化物のうち加水分解によりこれ以上簡単な化合物にならない糖を単糖類という。通常2～10の単糖からなる糖を少糖類（オリゴ糖ともいう）、それ以上の単糖からなる糖を多糖類というがその区別は明確ではない。

［徳久幸子］

多糖の分類

多糖はいろいろな観点から分類される。同一の単糖から構成されるものを単純多糖（ホモ多糖、ホモグリカンともいう）、異種の単糖から構成されるものを複合多糖（ヘテロ多糖、ヘテログリカンともいう）という。ウロン酸（アルドースの末端の-CH₂OHが酸化されてカルボキシ基-COOHとなった化合物）やエステル硫酸（糖のヒドロキシ基-OHに硫酸H₂SO₄が脱水結合した化合物）を多く含むものを酸性多糖という。中性糖のみのものは中性多糖という。ペントース（五炭糖ともいう）、ヘキソース（六炭糖ともいう）を構成糖とするホモ多糖をそれぞれペントサン、ヘキソサンという。ウロン酸とアミノ糖（糖のヒドロキシ基-OHをアミノ基-NH₂で置換した化合物）を構成糖とする一群の多糖はムコ多糖（グリコサミノグリカンともいう）とよばれる。脂質と結合した多糖は糖脂質（グリセロ糖脂質、スフィンゴ糖脂質など）に分類される。その他機能によって貯蔵多糖（デンプンなど）、構造多糖（セルロースなど）、機能多糖（ヘパリンなど）とよばれる。

［徳久幸子］

多糖の名称

構成糖の語尾の-oseを-anに変え、たとえばグルコースが構成糖のホモ多糖はグルカンglucanとよぶ。ヘテロ多糖は、構成単糖をアルファベット順に並べ、グリカンをつける。ガラクトマンノグリカンなどである。イヌリン、ペクチンなど慣用名でよばれるものも多い。

［徳久幸子］

多糖の性質

生体を構成する高分子物質で、タンパク質、脂質と並んで自然界にもっとも多く存在する。一般に無定形固体、水への溶解性はさまざまで、甘味はなく、フェーリング溶液（還元糖の検出と定量に用いる試薬）を還元しない。多糖は酸や酵素によって少糖（オリゴ糖）に分解される。それぞれの多糖に特異的な酵素が存在する。たとえばデンプン、グリコーゲン、セルロースはそれぞれ、アミラーゼ、グリコーゲンフォスフォリラーゼ、セルラーゼによって分解される。多糖の検出には、過ヨウ素酸でヒドロキシ基を酸化して、生じたアルデヒド基をシッフ試薬で呈色させる方法が用いられる。多糖の工業的利用は製紙、繊維、プラスチック、食品、医薬品など多岐にわたっている。

［徳久幸子］

『江上不二夫監修、鈴木旺他編『多糖生化学』（1969・共立出版）』▽『日本生化学会編『生化学データブック』（1979・縮刷版1981・東京化学同人）』▽『松田和雄編著『多糖の分離・精製法』（1987・学会出版センター）』▽『宮崎利夫編『多糖の構造と生理活性』（1990・朝倉書店）』▽『桜井直樹・山本良一・加藤陽治著『植物細胞壁と多糖類』（1991・培風館）』