title: Inhibition of α-amylase activity by cellulose: Kinetic analysis and nutritional implications.
abstract: We report on inhibition of α-amylase activity by cellulose based on in vitro experiments. The presence of cellulose in the hydrolysing medium reduced the initial velocity of starch hydrolysis in a concentration dependent manner. α-Amylase adsorption to cellulose was reversible, attaining equilibrium within 30min of incubation, and showed a higher affinity at 37°C compared to 20 and 0°C. The adsorption was almost unchanged in the presence of maltose (2.5-20mM) but was hindered in the presence of excess protein, suggesting non-specific adsorption of α-amylase to cellulose. Kinetic analyses of α-amylase hydrolysis of maize starch in the presence of cellulose showed that the inhibition is of a mixed type. The dissociation constant (Kic) of the EI complex was found to be ca. 3mg/mL. The observed inhibition of α-amylase activity suggests that cellulose in the diet can potentially attenuate starch hydrolysis.
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Qld 4072, Australia.
authors.forename: Sushil
authors.initials: S
authors.lastname: Dhital
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Qld 4072, Australia. Electronic address: m.gidley@uq.edu.au.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gidley
authors.affiliation: Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Qld 4072, Australia.
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Warren
mesh_terms: D000327:Adsorption; D002482:Cellulose / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008320:Maltose / Q000737:chemistry; D018613:Microscopy, Confocal; D012235:Rhodamines / Q000737:chemistry; D013213:Starch / Q000378:metabolism; D013696:Temperature; D003313:Zea mays / Q000378:metabolism; D000516:alpha-Amylases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D012235:Rhodamines; C009434:tetramethylrhodamine isothiocyanate; D008320:Maltose; D002482:Cellulose; D013213:Starch; D000516:alpha-Amylases
keywords: Adsorption isotherm; Alpha-amylase; Cellulose; Inhibition; Michaelis–Menten kinetics; Starch