The use of fluoro- and deoxy-substrate analogs to examine binding specificity and catalysis in the enzymes of the sorbitol pathway

Citation
Me. Scott et Re. Viola, The use of fluoro- and deoxy-substrate analogs to examine binding specificity and catalysis in the enzymes of the sorbitol pathway, CARBOHY RES, 313(3-4), 1998, pp. 247-253
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Agricultural Chemistry","Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
CARBOHYDRATE RESEARCH
ISSN journal
0008-6215 → ACNP
Volume
313
Issue
3-4
Year of publication
1998
Pages
247 - 253
Database
ISI
SICI code
0008-6215(199812)313:3-4<247:TUOFAD>2.0.ZU;2-4
Abstract
The carbohydrate specificity of the two enzymes that catalyze the metabolic interconversions in the sorbitol pathway, aldose reductase and sorbitol de hydrogenase, has been examined through the use of fluoro- and deoxy-substra te analogs. Hydrogen bonding has been shown to be the primary mode of inter action by which these enzymes specifically recognize and bind their respect ive polyol substrates. Aldose reductase has broad substrate specificity, an d all of the fluoro- and deoxysugars that were examined are substrates for this enzyme. Unexpectedly, both 3-fluoro- and 4-fluoro-D-glucose were found to be better substrates, with significantly lower K-m and higher k(cat)/K- m values than those of D-glucose. A more discriminating pattern of substrat e specificity is observed for sorbitol dehydrogenase. Neither the 2-fluoro nor the 2-deoxy analogs of D-glucitol were found to be substrates or inhibi tors, suggesting that the 2-hydroxyl group of sorbitol is a hydrogen bond d onor. The 4-fluoro and 4-deoxy analogs are poorer substrates than sorbitol, also implying a binding role for this hydroxyl group. In contrast, both 6- fluoro- and 6-deoxy-D-glucitol are very good substrates for sorbitol dehydr ogenase, indicating that the primary hydroxyl group at this position is not involved in substrate recognition by this enzyme. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.