Chemometric evaluation of enzymatic hydrolysis in the production of fish protein hydrolysates with acetylcholinesterase inhibitory activity

Identification of bioaccessible glycosylated neuroprotective peptides from brewer's spent yeast mannoproteins by in vitro and in silico studies

The aims of this work were to purify mannoproteins from brewer's spent yeast, to evaluate the neuroprotective and antioxidant properties of peptides generated by a simulated gastrointestinal digestion (SGID), and to identify the peptides responsible of acetylcholinesterase (AChE), tyrosinase (TYR), prolyl oligopeptidase (POP) and ABTS+ inhibitory activity using tandem mass spectrometry and in silico analysis. Mannoproteins from brewer's spent yeast were purified using the simultaneous effect of ethanol and pH on protein solubility followed by ultrafiltration process (10 kDa). The retained fraction (> 10 kDa) showed 80.5 ± 5.8 g protein 100 g-1 solids, of which 71.2 ± 1.0 g 100 g-1 were mannoprotein. The SGID of isolated mannoproteins released peptides with AChE, TYR, POP and ABTS+ inhibitory activity. Peptides released from mannoproteins showed strong inhibitory activity against TYR by diphenolase mechanism. These bioactivities were related to low MW mannose-linked peptides. After identification, the NEPGCYF peptide showed the highest in silico blood-brain barrier penetrating property (B3Pred score: 0.70) and in silico free radical scavenger activity (FRS score: 0.54) among mannose-linked peptides. Molecular docking indicated that this peptide acted as competitive inhibitor for AChE and POP enzymes, and as non-competitive inhibitor for TYR enzyme. These mechanisms were confirmed by in vitro kinetic analysis using the inhibitory mannose-linked peptides and the synthetic peptide NEPGCYF. Purified mannoproteins from brewer's spent yeast are a promising source of bioaccessible glycosylated peptides with good neuroprotective and antioxidant properties.

Preparation of Acetylcholinesterase Inhibitory Peptides from Yellowfin Tuna Pancreas Using Moderate Ultrasound-Assisted Enzymatic Hydrolysis

Bioactive peptides represent a promising therapeutic approach for Alzheimer's disease (AD) by maintaining cholinergic system homeostasis through the inhibition of acetylcholinesterase (AChE) activity. This study focused on extracting AChE inhibitory peptides from yellowfin tuna pancreas using moderate ultrasound-assisted enzymatic hydrolysis (MUE). Firstly, papain and MUE stood out from five enzymes and four enzymatic hydrolysis methods, respectively, by comparing the degree of hydrolysis and AChE inhibitory activity of different pancreatic protein hydrolysates. Subsequently, the optimal MUE conditions were obtained by single-factor, Plackett-Burman, and response surface methodologies. The pancreatic protein hydrolysate prepared under optimal MUE conditions was then purified by ultrafiltration followed by RP-HPLC, from which a novel AChE inhibitory peptide (LLDF) was identified by LC-MS/MS and virtual screening. LLDF effectively inhibited AChE activity by a competitive inhibition mechanism, with an IC50 of 18.44 ± 0.24 μM. Molecular docking and molecular dynamic simulation revealed that LLDF bound robustly to the active site of AChE via hydrogen bonds. These findings provided a theoretical basis for the valuable use of yellowfin tuna pancreas and introduced a new viewpoint on the potential therapeutic advantages of AChE inhibitory peptides for future AD treatment.

Computational approach based on freely accessible tools for antimicrobial drug design

Antimicrobial drug development is crucial for public health, especially with the emergence of pandemics and drug resistance that prompts the search for new therapeutic resources. In this context, in silico assays consist of a valuable approach in the rational drug design because they enable a faster and more cost-effective identification of drug candidates compared to in vitro screening. However, once a potential drug is identified, in vitro and in vivo assays are essential to verify the expected activity of the compound and advance it through the subsequent stages of drug development. This work aims to outline an in silico protocol that utilizes only freely available computational tools for identifying new potential antimicrobial agents, which is also suitable in the broad spectrum of drug design. Additionally, this paper reviews relevant computational methods in this context and provides a summary of information concerning the protein-ligand interaction.

Enzymatic Hydrolysis Systems Enhance the Efficiency and Biological Properties of Hydrolysates from Frozen Fish Processing Co-Products

Co-products from the frozen fish processing industry often lead to financial losses. Therefore, it is essential to transform these co-products into profitable goods. This study explores the production of fish protein hydrolysates (FPH) from three co-products: the heads and bones of black scabbardfish (Aphanopus carbo), the carcasses of gilthead seabream (Sparus aurata), and the trimmings of Nile perch (Lates niloticus). Four enzymatic hydrolysis systems were tested: an endopeptidase (Alcalase, A), an exopeptidase (Protana, P), two-stage hydrolysis with an endopeptidase followed by an exopeptidase (A + P), and a single stage with endo- and exopeptidase (AP). The results show that combined enzymatic treatments, especially single-stage Alcalase and Protana (AP), achieved high protein yields (80%) and enhanced degrees of hydrolysis (34 to 49%), producing peptides with lower molecular weights. FPH exhibited significant antioxidant activity, in 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, with EC50 values below 5 mg/mL. Additionally, AP hydrolysates demonstrated over 60% angiotensin-converting enzyme (ACE) inhibition at 5 mg/mL, indicating potential antihypertensive applications. Antidiabetic and anti-Alzheimer activities were present, but at relatively low levels. AP hydrolysates, especially from gilthead seabream, proved to be the most promising. This study highlights the value of fish co-products as sources of functional peptides, contributing to waste reduction, and their potential applications in food, agriculture, and nutraceuticals.

Optimization of the autolysis of rainbow trout viscera for amino acid release using response surface methodology

Background

Due to the huge amounts of their production in Europe, their environmental impact, and the difficulty in processing them, there is a clear necessity for the valorization of rainbow trout viscera. Considering that the production of fishmeal with viscera can be problematic, and in order to make viscera more profitable, the production of fish protein hydrolysates has been considered. Although silage and enzymatic hydrolysis are the most common methods for obtaining hydrolysates, autolysis has emerged as an alternative method that uses endogenous enzymes of the viscera.

Methods

Considering the stability and characteristics of the enzymes, a factorial design was carried out using three variables: pH, temperature, and water content. The design resulted in 15 experiments, and the results were analyzed using response surface methodology. The optimum parameters were validated by comparing the predicted outcomes with experimental results. Additionally, a kinetics study was conducted to shorten the autolysis time. Results from autolysis were compared with those from silage and enzymatic hydrolysis in a previous study.

Results

The optimal conditions for achieving the highest degree of hydrolysis and yield of free amino acids (FAAs) per 100 g of viscera and per total protein were determined to be a pH of 8, a temperature of 40 °C, and a water content of 6.85%. The pH and content of the added water were found to be significant variables during autolysis ( p < 0.05). The kinetic study showed that 7 h was still required to be effective.

Conclusions

Autolysis achieved a lower degree of hydrolysis than silage; however, as it solubilized more protein, the global yield of free amino acids per 100 g of viscera was slightly higher. It was concluded that endogenous alkaline proteases could be used in an autolytic process to obtain a free amino acid-rich hydrolysate from trout viscera.

Effects of walnut seed coat polyphenols on walnut protein hydrolysates: Structural alterations, hydrolysis efficiency, and acetylcholinesterase inhibitory capacity

The walnut meal is rich in nutrients such as protein from the kernel and polyphenolic compounds from the seed coat. However, the influences of seed coat polyphenols on walnut protein (WP) hydrolysis remained unclear. In this study, our findings indicated that polyphenols induced alterations in the secondary structure and amino acid composition of WP. These changes resulted in both a hindrance of hydrolysis and an enhancement of acetylcholinesterase (AChE) inhibition. Furthermore, four peptides of 119 identified peptides (LR, SF, FQ, and FR) were synthesized based on higher predicted bioactivity and Vinascores in silico. Among them, FQ showed interaction with amino acid residues in AChE through the formation of four π-π stacking bonds and two hydrogen bonds, resulting in the highest AChE inhibitory capacity. The combination index showed that chlorogenic acid derived from the seed coat and FQ at the molar ratio of 1:4 exhibited synergistic effects of AChE inhibition.

Comparison of amino acid release between enzymatic hydrolysis and acid autolysis of rainbow trout viscera

Fish protein hydrolysates were obtained from cultured rainbow trout (Oncorhynchus mykiss) viscera using commercial and endogenous enzymes. Two methods were employed for hydrolysis: acid autolysis (also known as silage) at room temperature for 10 days in acidic conditions, until total solubilisation, and enzymatic hydrolysis using Alcalase 2.4 LFG, Protana Prime, and the endogenous enzymes in the viscera. The effectiveness of both methods in releasing free amino acids (FAA) was assessed. After evaluating the results, the most effective enzymatic hydrolysis was optimized. The findings indicated that enzymatic hydrolysis with Alcalase, Protana Prime and endogenous enzymes combined for 7 h at a dose of 1% of protein, and a 7-day acid autolysis yielded the highest degree of hydrolysis (83.8% and 75.8%), a yield of FAA from viscera of 5.9% and 3.2%, and a yield of FAA from total protein of 71.3% and 52.5%, respectively. In conclusion, the use of commercial enzymes was more efficient in releasing amino acids, but endogenous enzymes showed a strong proteolytic capacity during acid autolysis, suggesting it also as a promising method to produce FAA-rich hydrolysates.

Anticholinesterase Inhibition, Drug-Likeness Assessment, and Molecular Docking Evaluation of Milk Protein-Derived Opioid Peptides for the Control of Alzheimer’s Disease

The drug-likeness and pharmacokinetic properties of 23 dairy-protein-derived opioid peptides were studied using SwissADME and ADMETlab in silico tools. All the opioid peptides had poor drug-like properties based on violations of Lipinski’s rule-of-five. Moreover, prediction of their pharmacokinetic properties showed that the peptides had poor intestinal absorption and bioavailability. Following this, two well-known opioid peptides (βb-casomorphin-5, βb-casomorphin-7) from A1 bovine milk and caffeine (positive control) were selected for in silico molecular docking and in vitro inhibition study with two cholinesterase enzyme receptors important for the pathogenesis of Alzheimer’s disease. Both peptides showed higher binding free energies and inhibitory activities to butyrylcholinesterase (BChE) than caffeine, but in vitro binding energy values were lower than those from the docking model. Moreover, the two casomorphins had lower inhibitory properties against acetylcholinesterase (AChE) than caffeine, although the docking model predicted the opposite. At 1 mg/mL concentrations, βb-casomorphin-5 and βb-casomorphin-7 showed promising results in inhibiting both cholinesterases (i.e., respectively 34% and 43% inhibition of AChE, and 67% and 81% inhibition of BChE). These dairy-derived opioid peptides have the potential to treat Alzheimer’s disease via cholinesterase inhibition. However, appropriate derivatization may be required to improve their poor predicted intestinal absorption and bioavailability.