翻訳と辞書 |
Glycoside hydrolase family 20 : ウィキペディア英語版 | Glycoside hydrolase family 20
In molecular biology, glycoside hydrolase family 20 is a family of glycoside hydrolases. Glycoside hydrolases are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families.〔(Bairoch, A. "Classification of glycosyl hydrolase families and index of glycosyl hydrolase entries in SWISS-PROT". 1999. )〕 This classification is available on the CAZy(http://www.cazy.org/GH1.html) web site,〔(Henrissat, B. and Coutinho P.M. "Carbohydrate-Active Enzymes server". 1999. )〕 and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.〔(CAZypedia, an online encyclopedia of carbohydrate-active enzymes. )〕 Glycoside hydrolase family 20 (CAZY GH_20 ) comprises enzymes with several known activities; beta-hexosaminidase (); lacto-N-biosidase (). Carbonyl oxygen of the C-2 acetamido group of the substrate acts as the catalytic nucleophile/base in this family of enzymes. In the brain and other tissues, beta-hexosaminidase A degrades GM2 gangliosides; specifically, the enzyme hydrolyses terminal non-reducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides. There are 3 forms of beta-hexosaminidase: hexosaminidase A is a trimer, with one alpha, one beta-A and one beta-B chain; hexosaminidase B is a tetramer of two beta-A and two beta-B chains; and hexosaminidase S is a homodimer of alpha chains. The two beta chains are derived from the cleavage of a precursor. Mutations in the beta-chain lead to Sandhoff disease, a lysosomal storage disorder characterised by accumulation of GM2 ganglioside. ==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Glycoside hydrolase family 20」の詳細全文を読む
スポンサード リンク
翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|