{"title":"Study on the role of tyrosine side-chains at the active centre of emulsin β-d-glucosidase","authors":"László Kiss, Ibolya Kóródi, Pál Nánási","doi":"10.1016/0005-2744(81)90043-7","DOIUrl":null,"url":null,"abstract":"<div><p>The role of exposed tyrosine side-chains in enzyme-catalyzed reaction by sweet almond emulsion β-<span>d</span>-glucosidase (β-<span>d</span>-glucoside glucohydrolase, EC 3.2.1.21) has been studied using <em>N</em>-acetylimidazole as the specific reagent. The changes in activity, binding affinity and kinetic parameters (<em>K</em><sub>m</sub>, <em>V</em>) as a result of acetylation of the phenolic hydroxyl groups have been determined. The acetylation increased the <em>K</em><sub>m</sub> values of both β-glucosidase and β-galactosidase activities, whereas <em>V</em> remained unchanged. Similarly, the binding affinity for immobilized phenyl β-<span>d</span>-glucopyranoside decreased appreciably. After the removal of the acetyl groups the enzyme regained 96% of the original activity. It is concluded that the tyrosine moieties, located in the active centre of the enzyme, have both glucoside and galactoside binding functions.</p></div>","PeriodicalId":100159,"journal":{"name":"Biochimica et Biophysica Acta (BBA) - Enzymology","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1981-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0005-2744(81)90043-7","citationCount":"4","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochimica et Biophysica Acta (BBA) - Enzymology","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0005274481900437","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 4
Abstract
The role of exposed tyrosine side-chains in enzyme-catalyzed reaction by sweet almond emulsion β-d-glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21) has been studied using N-acetylimidazole as the specific reagent. The changes in activity, binding affinity and kinetic parameters (Km, V) as a result of acetylation of the phenolic hydroxyl groups have been determined. The acetylation increased the Km values of both β-glucosidase and β-galactosidase activities, whereas V remained unchanged. Similarly, the binding affinity for immobilized phenyl β-d-glucopyranoside decreased appreciably. After the removal of the acetyl groups the enzyme regained 96% of the original activity. It is concluded that the tyrosine moieties, located in the active centre of the enzyme, have both glucoside and galactoside binding functions.