title: Epigallocatechin-3-gallate inhibits lactase but is alleviated by salivary proline-rich proteins.
abstract: Lactase phlorizin hydrolase is a small intestinal brush border enzyme that catalyzes the hydrolysis of the milk sugar, lactose, and also many flavonoid glucosides. We demonstrate that epigallocatechin-3-gallate (EGCG), the principal flavonoid from green tea, inhibits in vitro hydrolysis of lactose by intestinal lactase. We then tested the hypothesis that salivary proline-rich proteins (PRPs) could modulate this inhibition and stabilize EGCG. Inhibition by EGCG of digestive enzymes (α-amylase>chymotrypsin>trypsin>lactase≫pepsin) was alleviated ∼2-6-fold by PRPs. Furthermore, PRPs appeared stable to proteolysis and also stabilized EGCG under digestive conditions in vitro. This is the first report on EGCG inhibition of lactase, and it quantifies the protective role of PRPs against EGCG inhibition of digestive enzymes.
authors.affiliation: Department of Food Science and Technology, University of Karachi, Karachi 75270, Pakistan.
authors.forename: Shahina
authors.initials: S
authors.lastname: Naz
authors.forename: Rahmanullah
authors.initials: R
authors.lastname: Siddiqi
authors.forename: Tristan P
authors.initials: TP
authors.lastname: Dew
authors.forename: Gary
authors.initials: G
authors.lastname: Williamson
mesh_terms: D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D002417:Cattle; D004063:Digestion; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007421:Intestine, Small / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D007700:Kinetics; D043322:Lactase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D008954:Models, Biological; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D055273:Salivary Proline-Rich Proteins / Q000737:chemistry / Q000378:metabolism*; D013662:Tea / Q000737:chemistry
chemical_list: D004791:Enzyme Inhibitors; D010936:Plant Extracts; D055273:Salivary Proline-Rich Proteins; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate; D043322:Lactase; D007785:Lactose