Exploring the factors that affect the themostability of barley limit dextrinase - Inhibitor complex

Precise Immobilization Strategy Combined with Rational Design to Improve β-Agarase Stability

Recently, the orientational immobilization of enzymes has attracted extensive attention. In this study, we report the development of a strategy combined with rational design to achieve precise site-specific covalent immobilization of β-agarase. We first rationally screened six surface sites that can be mutated to cysteine by combining molecular dynamics simulation and energy calculation. Site-specific immobilization was successfully achieved by Michael addition reaction of mutant enzymes and maleimide-modified magnetic nanoparticles (MAL-MNPs). The enzyme activity retention rate of R66C-MAL-MNPs and K588C-MAL-MNPs was greater than 96%. The thermal deactivation kinetics study revealed that the site-specific immobilization strategy significantly improved the thermal stability of Aga50D, resulting in a substantial increase in its antidenaturation activity at elevated temperatures, and the highest t1/2 of the immobilized mutant enzymes was increased by an impressive 21.25-fold at 40 °C. The immobilized mutant enzymes also showed significantly enhanced tolerance to metal ions and organic reagents. For instance, all of the immobilized enzymes maintained over 90% of their enzymatic activity in the 50% (v/v) acetone/water solution. The present work may pave the way for the design of precisely immobilized enzymes, which can help promote green manufacturing.

Statistical Characterization of Food-Derived α-Amylase Inhibitory Peptides: Computer Simulation and Partial Least Squares Regression Analysis

α-Amylase inhibitory peptides are used to treat diabetes, but few studies have statistically characterized their interaction with α-amylase. This study performed the molecular docking of α-amylase with inhibitory peptides from published papers. The key sites, side chain chargeability, and hydrogen bond distribution characteristics were analyzed. Molecular dynamics simulated the role of key sites in complex stability. Moreover, partial least squares regression (PLSR) was used to analyze the contribution of different amino acids in the peptides to inhibition. The results showed that, for the α-amylase molecule, His201 and Gln63, with the highest interaction numbers (INs, 15, 15) and hydrogen bond values (HBVs, 11.50, 10.33), are the key sites on α-amylase, and amino acids with positively charged side chains were important for inhibitory activity. For the inhibitory peptides, Asp and Arg had the highest HBVs, and amino acids with charged side chains were more likely to form hydrogen bonds and exert inhibitory activity. In molecular dynamics simulations, peptides involving key binding sites formed more stable complexes with α-amylase than α-amylase alone, suggesting enhanced inhibitory effects. Further, PLSR results showed that amino acids close to the N-terminus of the inhibitory peptide, located in the third and fifth positions, were significantly correlated with its inhibitory activity. In conclusion, this study provides a new approach to developing and screening α-amylase inhibitors.

Post-sprouting thermal treatment of green barley malt to produce functional clean-label ingredients: Impact on fermentation, bread-making properties and bread quality

Malt flour represents a potential clean label bread improver, but a high enzymatic activity can lead to some bread defects. Thus, this study was focused on applying different thermal treatments (10 and 40 min; 70-90 °C) to green barley malt in order to promote a partial enzyme inactivation. The addition of 1.5 g of thermally treated malt (TTM) per 100 g of flour in wheat bread formulation was evaluated regarding the resulting bread-making properties, dough fermentation and overall bread quality. Activity of starch-degrading enzymes was not detectable above 80 °C/10 min. TTM incorporation improved the gas production by up to 60% during fermentation, mainly in formulations to which malts thermally treated under mild conditions have been added. Compared to untreated malt, thermal treatment reduced dough thermal weakening, improved gel strength during gelatinization and maintained low setback values. Bread collapse observed by baking follow-up was related to gas inflation and low mechanical resistance. Formulations with the addition of malts thermally treated at 70 °C for 40 min resulted in breads with higher specific volume, improved coloration and a crumb with slightly smaller pores than control and untreated malts. Thus, thermal treatment can be used as a technique to produce standardized malted flour to be used as clean label bread improvers.