The effect of konjac glucomannan on enzyme kinetics and fluorescence spectrometry of digestive enzymes: An in vitro research from the perspective of macromolecule crowding.

Note: Konjac glucomannan with different molecular weight and the digestive enzyme molecules are depicted by spheres and small irregular shapes, respectively. The arrows represent the digestive enzyme diffusion trajectories. The increased molecular weight and the degree of crowding of konjac glucomannan results in changes in the kinetics and conformation of digestive enzyme molecules. [Display omitted] • The MMC effect induced by KGM could be regulated by the change of MW. • The stronger MMC induced by KGM had a higher ability to inhibit the digestion. • MMC induced by KGM decreased the Michaelis-Menten constants of digestive enzymes. • MMC induced by KGM changed the conformation of digestive enzymes. Konjac glucomannan (KGM) can significantly prolong gastrointestinal digestion. However, it is still worth investigating whether the macromolecular crowding (MMC) induced by KGM is correlated with digestion. In this paper, the MMC effect was quantified by fluorescence resonance energy transfer and microrheology, and the digests of starch, protein, and oil were determined. The digestive enzymes were analyzed by enzyme reaction kinetic and fluorescence quenching. The results showed that higher molecular weight (604.85 ∼ 1002.21 kDa) KGM created a larger MMC (>0.8), and influenced the digestion of macronutrients; the digests of starch, protein, and oil all decreased significantly. MMC induced by KGM decreased the Michaelis-Menten constants (K m and V max) of pancreatic α-amylase (PPA), pepsin (PEP), and pancreatic lipase (PPL). The larger MMC (>0.8) induced by KGM resulted in the decrease of fluorescence quenching constants (K sv) in PPA and PPL, and the increase of K sv in PEP. Therefore, varying degrees of MMC induced by KGM could play a role in regulating digestion and the inhibitory effect on digestion was more significant in a relatively more crowded environment induced by KGM. This study provides theoretical support for the strategies of nutrient digestion regulation from the perspective of MMC caused by dietary fiber. [ABSTRACT FROM AUTHOR]