title: Measurement of the activity of polyuronic acid C-5 epimerases.
abstract: A relatively simple assay procedure for measuring the reactions catalyzed by polyuronic acid C-5 epimerases has been developed. Action of C-5 epimerases inverts the C-6 carboxyl group of polyuronic acids converting beta-linked residues into alpha-linked residues or vice versa. The assay takes advantage of the greater susceptibility of the acid hydrolysis of alpha-glycosidic linkages than beta-glycosidic linkages. The method involves the partial acid hydrolysis of the polyuronic acid before and after reaction with the C-5 epimerase. The greater or lesser amounts of uronic acid released (solubilized) before and after reaction of the C-5 epimerase are a measure of the amount of alpha- or beta-glycosidic linkages that are formed and a measure of the amount of catalysis by the enzyme.
authors.affiliation: Laboratory of Carbohydrate Chemistry and Enzymology, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: P S
authors.initials: PS
authors.lastname: Chang
authors.forename: R
authors.initials: R
authors.lastname: Mukerjea
authors.forename: J F
authors.initials: JF
authors.lastname: Robyt
mesh_terms: D000464:Alginates / Q000737:chemistry; D016948:Azotobacter vinelandii / Q000201:enzymology; D002236:Carbohydrate Conformation; D002238:Carbohydrate Epimerases / Q000032:analysis* / Q000378:metabolism; D005965:Glucuronates / Q000032:analysis / Q000378:metabolism; D020723:Glucuronic Acid; D006603:Hexuronic Acids / Q000032:analysis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D013053:Spectrophotometry; D014574:Uronic Acids / Q000737:chemistry
chemical_list: D000464:Alginates; D005965:Glucuronates; D006603:Hexuronic Acids; D014574:Uronic Acids; C007896:guluronic acid; D020723:Glucuronic Acid; D002238:Carbohydrate Epimerases; C022419:polymannuronic acid 5-epimerase