Enzyme kinetic approach for mechanistic insight and predictions of in vivo starch digestibility and the glycaemic index of foods

Peter J Butterworth; Balázs H Bajka; Cathrina H Edwards; Frederick J Warren; Peter R Ellis

doi:10.1016/j.tifs.2021.11.015

Enzyme kinetic approach for mechanistic insight and predictions of in vivo starch digestibility and the glycaemic index of foods

Trends Food Sci Technol. 2022 Feb:120:254-264. doi: 10.1016/j.tifs.2021.11.015.

Authors

Peter J Butterworth¹, Balázs H Bajka¹, Cathrina H Edwards², Frederick J Warren², Peter R Ellis¹

Affiliations

¹ Biopolymers Group, Departments of Biochemistry and Nutritional Sciences, Faculty of Life Sciences and Medicine, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, UK.
² Quadram Institute Bioscience, Rosalind Franklin Road, Norwich Research Park, Norwich, NR4 7UQ, UK.

Abstract

Background: Starch is a principal dietary source of digestible carbohydrate and energy. Glycaemic and insulinaemic responses to foods containing starch vary considerably and glucose responses to starchy foods are often described by the glycaemic index (GI) and/or glycaemic load (GL). Low GI/GL foods are beneficial in the management of cardiometabolic disorders (e.g., type 2 diabetes, cardiovascular disease). Differences in rates and extents of digestion of starch-containing foods will affect postprandial glycaemia.

Scope and approach: Amylolysis kinetics are influenced by structural properties of the food matrix and of starch itself. Native (raw) semi-crystalline starch is digested slowly but hydrothermal processing (cooking) gelatinises the starch and greatly increases its digestibility. In plants, starch granules are contained within cells and intact cell walls can limit accessibility of water and digestive enzymes hindering gelatinisation and digestibility. In vitro studies of starch digestion by α-amylase model early stages in digestion and can suggest likely rates of digestion in vivo and expected glycaemic responses. Reports that metabolic responses to dietary starch are influenced by α-amylase gene copy number, heightens interest in amylolysis.

Key findings and conclusions: This review shows how enzyme kinetic strategies can provide explanations for differences in digestion rate of different starchy foods. Michaelis-Menten and Log of Slope analyses provide kinetic parameters (e.g., K _m and k _cat /K _m ) for evaluating catalytic efficiency and ease of digestibility of starch by α-amylase. Suitable kinetic methods maximise the information that can be obtained from in vitro work for predictions of starch digestion and glycaemic responses in vivo.

Keywords: AMY1, human salivary α-amylase gene; AMY2, human pancreatic α-amylase gene; Alpha-amylase; BMI, body mass index; CE, catalytic efficiency; CVD, cardiovascular disease; Enzyme kinetics; Fto, alpha-oxoglutarate-dependent dioxygenase gene; GI, glycaemic index; GIT, gastrointestinal tract; GL, glycaemic load; GLUT2, glucose transporter 2; Gene copy number; HI, hydrolysis index; IC50, inhibitor concentration causing 50% inhibition; LOS, logarithm of slope plot; Metabolic significance; RDS, rapidly digestible starch; RS, resistant starch; Resistant starch; SCFAs, short chain fatty acids; SDS, slowly digestible starch; SGLT1, sodium-dependent glucose co-transporter; Starch digestion; XRD, X-ray diffraction.

Publication types

Review