3 or 3′-Galloyl substitution plays an important role in association of catechins and theaflavins with porcine pancreatic α-amylase: The kinetics of inhibition of α-amylase by tea polyphenols. (October 2016)

• Record Type: Journal Article
• Authors: Sun, Lijun; Warren, Fredrick J.; Netzel, Gabriele; Gidley, Michael J.
• Is Part Of: Journal of functional foods. Volume 26(2016)
• Page Start: 144
• Page End: 156
• Publication Date: 2016-10
• Subjects: Tea polyphenols -- α-Amylase -- Inhibition -- Kinetics -- Galloyl moiety; TEs tea extracts -- PPA porcine pancreatic α-amylase -- GTE green tea extracts -- BTE black tea extracts -- OTE oolong tea extracts -- CF caffeine -- GA gallic acid -- TA tannic acid -- C catechin -- EC epicatechin -- EGC epigallocatechin -- EGCG epigallocatechin gallate -- ECG epicatechin gallate -- TF theaflavin -- TF1 theaflavin-3′-gallate -- TF2 theaflavin-3, 3′-digallate -- Kic the competitive inhibition constant -- Kiu the uncompetitive inhibition constant -- Kmapp the apparent Michaelis constant -- Vmaxapp the apparent maximum initial reaction velocity; Functional foods -- Analysis -- Periodicals; Food -- Biotechnology -- Periodicals; Nutrition -- Periodicals; 613.2
• DOI: 10.1016/j.jff.2016.07.012
• Languages: English
• ISSNs: 1756-4646

Abstract

Highlights: α-Amylase activity was inhibited by three tea extracts and phenolic compounds in teas. Only catechins with a galloyl substituent at the 3-position showed measurable inhibition. 3 and 3′ Galloyl substitution increase the inhibitory activity of theaflavins. 3 or 3′ Galloyl substitution increase the association of catechins and theaflavins with amylase. There is a linear correlation between IC50 and inhibition constants ( Kic and Kiu ). Abstract: The inhibitory activities of three tea extracts (TEs) and individual phenolic compounds in TEs against porcine pancreatic α-amylase (PPA) were studied by measuring their half inhibitory (IC50 ) concentrations. The kinetics of inhibition by these extracts and compounds were investigated through Dixon, Cornish-Bowden, and Lineweaver–Burk plots. The results showed that green, oolong and black tea extracts, epigallocatechin gallate, theaflavin-3, 3′-digallate and tannic acid were competitive inhibitors of PPA, whereas epicatechin gallate, theaflavin-3′-gallate and theaflavin were mixed-type inhibitors with both competitive and uncompetitive inhibitory characteristics. Only catechins with a galloyl substituent at the 3-position showed measurable inhibition. The competitive inhibition constants ( Kic ) were lower for theaflavins than catechins, with the lowest value for theaflavin-3, 3′-digallate. The lower Kic than the uncompetitive inhibition constant for the mixed-type inhibitors suggests that they bind more tightly with free PPA than with the PPA–starch complex. A 3 and/or 3′-galloyl moiety in catechin and theaflavin structures was consistently found to increase inhibition of PPA through enhanced association with the enzyme active site.