The biological role of prolyl oligopeptidase and the procognitive potential of its peptidic inhibitors from food proteins.

Prolyl oligopeptidase (POP) is a conserved serine protease belonging to proline-specific peptidases. It has both enzymatic and non-enzymatic activity and is involved in numerous biological processes in the human body, playing a role in e.g., cellular growth and differentiation, inflammation, as well as the development of some neurodegenerative and neuropsychiatric disorders. This article describes the physiological and pathological aspects of POP activity and the state-of-art of its peptidic inhibitors originating from food proteins, with a particular focus on their potential as cognition-enhancing agents. Although some milk, meat, fish, and plant protein-derived peptides have the potential to be applied as natural, procognitive nutraceuticals, their effectiveness requires further evaluation, especially in clinical trials. We demonstrated that the important features of the most promising POP-inhibiting peptides are very short sequence, high content of hydrophobic amino acids, and usually the presence of proline residue.

Antioxidant peptides: Overview of production, properties, and applications in food systems.

In recent years, several studies have reported the beneficial effects of antioxidant peptides in delaying oxidation reactions. Thus, a growing number of food proteins have been investigated as suitable sources for obtaining these antioxidant peptides. In this study, some of the most critical developments in the discovery of peptidic antioxidants are discussed. Initially, the primary methods to release, purify, and identify these antioxidant peptides from various food-derived sources are reviewed. Then, computer-based screening methods of the available peptides are summarized, and methods to interpret their structure-activity relationship are illustrated. Finally, approaches to the large-scale production of these bioactive peptides are described. In addition, the applications of these antioxidants in food systems are discussed, and gaps, future challenges, and opportunities in this field are highlighted. In conclusion, various food items can be considered promising sources to obtain these novel antioxidant peptides, which present various opportunities for food applications in addition to health promotion. The lack of in-depth data on the link between the structure and activity of these antioxidants, which is critical for the prediction of possible bioactive amino acid sequences and their potency in food systems and in vivo conditions (rather than in vitro systems), requires further attention. Consequently, future collaborative research activities between the industry and academia are required to realize the commercialization objectives of these novel antioxidant peptides.

Enhancing activity of food protein-derived peptides: An overview of pretreatment, preparation, and modification methods.

Food protein-derived peptides have garnered considerable attention due to their potential bioactivities and functional properties. However, the limited activity poses a challenge in effective utilization aspects. To overcome this hurdle, various methods have been explored to enhance the activity of these peptides. This comprehensive review offers an extensive overview of pretreatment, preparation methods, and modification strategies employed to augment the activity of food protein-derived peptides. Additionally, it encompasses a discussion on the current status and future prospects of bioactive peptide applications. The review also addresses the standardization of mass production processes and safety considerations for bioactive peptides while examining the future challenges and opportunities associated with these compounds. This comprehensive review serves as a valuable guide for researchers in the food industry, offering insights and recommendations to optimize the production process of bioactive peptides.

Cross-seeding of alpha-synuclein aggregation by amyloid fibrils of food proteins.

The aggregation of the protein α-synuclein (aSyn) into amyloid fibrils in the human brain is associated with the development of several neurodegenerative diseases, including Parkinson's disease. The previously observed prion-like spreading of aSyn aggregation throughout the brain and the finding that heterologous cross-seeding of amyloid aggregation occurs in vitro for some proteins suggest that exposure to amyloids in general may pose a risk for disease development. To elucidate which protein fibril characteristics determine if and how heterologous amyloid seeding can occur, we investigated the potential of amyloid fibrils formed from proteins found in food, hen egg white lysozyme, and bovine milk ß-lactoglobulin to cross-seed aSyn aggregation in the test tube. We observed that amyloid fibrils from lysozyme, but not ß-lactoglobulin, potently cross-seeded the aggregation of aSyn as indicated by a significantly shorter lag phase of aSyn aggregation in the presence of lysozyme fibrils. The cross-seeding effect of lysozyme was found to be primarily driven by a surface-mediated nucleation mechanism. The differential seeding effect of lysozyme and ß-lactoglobulin on aSyn aggregation could be explained on the basis of binding affinity, binding site, and electrostatic interactions. Our results indicate that heterologous seeding of proteins may occur depending on the physicochemical characteristics of the seed protein fibril. Our findings suggest that heterologous seeding has the potential to determine the pathogenesis of neurodegenerative amyloid diseases.

Quantification of Protein "Biomarkers" in Wheat-Based Food Systems: Dealing with Process-Related Issues.

Selected food proteins may represent suitable markers for assessing either the presence/absence of specific food ingredients or the type and intensity of food processes. A fundamental step in the quantification of any protein marker is choosing a proper protocol for solubilizing the protein of interest. This step is particularly critical in the case of solid foods and when the protein analyte is prone to undergo intermolecular disulfide exchange reactions with itself or with other protein components in the system as a consequence of process-induced unfolding. In this frame, gluten-based systems represent matrices where a protein network is present and the biomarker proteins may be either linked to other components of the network or trapped into the network itself. The protein biomarkers considered here were wheat gluten toxic sequences for coeliac (QQPFP, R5), wheat germ agglutinin (WGA), and chicken egg ovalbumin (OVA). These proteins were considered here in the frame of three different cases dealing with processes different in nature and severity. Results from individual cases are commented as for: (1) the molecular basis of the observed behavior of the protein; (2) the design of procedure aimed at improving the recovery of the protein biomarker in a form suitable for reliable identification and quantification; (3) a critical analysis of the difficulties associated with the plain transfer of an analytical protocol from one product/process to another. Proper respect for the indications provided by the studies exemplified in this study may prevent coarse errors in assays and vane attempts at estimating the efficacy of a given treatment under a given set of conditions. The cases presented here also indicate that recovery of a protein analyte often does not depend in a linear fashion on the intensity of the applied treatment, so that caution must be exerted when attributing predictive value to the results of a particular study.

Formulation, optimization, and characterization of whey protein isolate nanocrystals for celecoxib delivery.

AIM: Current study aimed to improve the solubility and release profile of the celecoxib for cancer application. However, the low water solubility of celecoxib limited its application for cancer chemotherapy. Hence, new drug delivery-based approaches are compulsory for the efficient delivery of hydrophobic celecoxib for chemotherapy. METHODS: The celecoxib-loaded nanocrystals were prepared by anti-solvent precipitation-ultrasonication technique, and the formulation was optimised through various process parameters. RESULTS: The optimised formulation had an average particle diameter of 171.09 ± 6.23 nm, with a PDI of 0.123 ± 0.009 and high ZP -27.3 ± 0.2 mV. The optimised formulation was stable, had higher entrapment efficiency 97.26 ± 1.12%. The conformational changes in the denatured protein solution were detected through fluorescence spectroscopy. The transmission electron microscopy investigation showed rod-shaped nanocrystals morphology, and no chemical interactions were observed in optimised formulation through FTIR. The DSC and PXRD analysis exhibited an amorphous state of the freeze-dried formulation drug. Also, optimised nanocrystals enhance drug solubility around 26.01-fold, 15.51-fold and 19.08-fold in purified water, pH 6.8 and pH 7.4, and accomplish sustained drug delivery, respectively. CONCLUSION: It can be concluded that biopolymer-coated celecoxib nanocrystals might be potential drug delivery of hydrophobic molecules for cancer therapy.

Cell-envelope proteinases from lactic acid bacteria: Biochemical features and biotechnological applications.

Proteins displayed on the cell surface of lactic acid bacteria (LAB) perform diverse and important biochemical roles. Among these, the cell-envelope proteinases (CEPs) are one of the most widely studied and most exploited for biotechnological applications. CEPs are important players in the proteolytic system of LAB, because they are required by LAB to degrade proteins in the growth media into peptides and/or amino acids required for the nitrogen nutrition of LAB. The most important area of application of CEPs is therefore in protein hydrolysis, especially in dairy products. Also, the physical location of CEPs (i.e., being cell-envelope anchored) allows for relatively easy downstream processing (e.g., extraction) of CEPs. This review describes the biochemical features and organization of CEPs and how this fits them for the purpose of protein hydrolysis. It begins with a focus on the genetic organization and expression of CEPs. The catalytic behavior and cleavage specificities of CEPs from various LAB are also discussed. Following this, the extraction and purification of most CEPs reported to date is described. The industrial applications of CEPs in food technology, health promotion, as well as in the growing area of water purification are discussed. Techniques for improving the production and catalytic efficiency of CEPs are also given an important place in this review.

Extraction and Characterization of Proteins from Pachyrhizus ahipa Roots: an Unexploited Protein-Rich Crop.

Pachyrhizus ahipa is an unexploited crop known to be rich in proteins compared to other edible roots and tubers. These proteins are not prolamins, thus ahipa represents an interesting new source of ingredients for gluten-free foods. In this work, ahipa proteins (AP) were extracted and partially characterized in pursuit of their use as food ingredients. The effect of ultrasound treatment on protein extraction efficiency was evaluated. AP were characterized by their size, amino acid composition, surface hydrophobicity, intrinsic fluorescence, FTIR spectra, solubility, and thermal and emulsifying properties. AP were efficiently removed from the vegetal tissue using PBS or water, regardless of the use of ultrasound, but not easily recovered by precipitation. This protein fraction was composed of small proteins, with sizes ranging from 9 to 30 kDa, and highly polar. AP resulted particularly rich in aspartic acid (59% of the total amino acid content), for which they can be classified as Asp-rich proteins. Their elevated content of acidic groups was evidenced in the ATR-FTIR spectrum. The amide I band deconvolution as well as the low surface hydrophobicity and denaturation enthalpy indicated that these proteins are mainly unordered structures. The emulsifying properties of AP were enhanced when the concentration was increased from 0.1 to 1% (w/v) but resulted lower than those of soy protein. The high polarity, small size, and low isoelectric point make AP particularly suitable for acidic food matrices.

Innovation in the food industry using microbial transglutaminase: Keys to success and future prospects.

Transglutaminase (TG) catalyzes cross-linking between the γ-carboxyamide groups of glutamine residues and the ε-amino groups of lysine residues in polypeptide chains, yielding ε- (γ-glutamyl) lysine (G-L) bonds. By forming a network structure in the protein via G-L bonds, it is possible to increase the viscosity of protein solutions or to cause gelation. Nearly thirty years have passed since microbial TG (MTG) appeared in the food enzyme market. Since the start of research and development, MTG has been used in fishery products such as kamaboko (boiled fish paste), meat products such as sausages, milk products such as yogurt, processed-soybean products such as tofu, and wheat products such as bread and noodles. MTG has provided effects such as adding new functions and reducing waste in food applications. The purpose of this review is to describe not only the history of research and development of TG but also the key aspects that have facilitated the great success of this process as a technology for enzymatically modifying protein-containing foods.

Evidence runs contrary to digestive stability predicting protein allergenicity.

A dogma has persisted for over two decades that food allergens are more stable to digestion compared with non-allergenic proteins. This belief has become enshrined in regulations designed to assess the allergenic risk of novel food proteins. While the empirical evidence accumulated over the last 20+ years has largely failed to confirm a correlation between digestive stability and the allergenic status of proteins, even those who accept this finding often assert that this shortfall is the result of faulty assay design rather than lack of causality. Here, we outline why digestive stability may not in fact correlate with allergenic potential.

Natural ingredients in cosmetic products-A suggestion for a screening series for skin allergy.

BACKGROUND: Naturally derived cosmetic product ingredients of both plant and animal origin are being included increasingly in product formulations in order to cater to consumer preferences. They may be an overlooked cause of reactions to cosmetic products in some patients with dermatitis. OBJECTIVES: To identify naturally derived cosmetic product ingredients with allergenic potential (type I and type IV) and propose a cosmetic screening test series. METHODS: The study was conducted in two steps. The first step was a market survey using a nonprofit application helping consumers avoid problematic substances in cosmetic products. The application contained 10 067 cosmetic products that were label checked for naturally derived cosmetic product ingredients. The second step was a literature search to examine how frequently the naturally derived ingredients were described and related to allergic reactions in cosmetics or other topically administered products. RESULTS: We identified 121 different naturally derived cosmetic product ingredients that were included in at least 30 cosmetic products. In total, 22 ingredients were selected for a screening test series. CONCLUSIONS: We propose a supplemental patch test and a prick test screening series with naturally derived cosmetic product ingredients for patients with skin reactions to cosmetic products, aiming to identify a cause in more patients than is currently possible.

ATPS: "Aqueous two-phase system" as the "answer to protein separation" for protein-processing food industry.

Every individual needs food for its nutritional value and flavor while the economic growth of a nation depends on a thriving profit-generating industry. The food industry caters to both needs in an efficient manner. Proteins can rightly be considered as the driving force behind the overwhelming success of this industry. However, purification of proteins is not an easy undertaking due to their intricate nature while presently employed procedures for this purpose, regrettably, are both costly, and labor- and time-intensive in addition to being unsettling on proteins structural conformity. ATPS has accumulated a lot of interest from the scientific community due to its mild operating conditions, high recovery yield, ease of scaling it up, and its cost-effective and environment friendly nature. This review tries to amass some accounts concerning the utility of ATPS for the separation and purification of proteins. Some auspicious clues in this regard can be witnessed along with a few loopholes which need to be addressed before this technique can truly demonstrate its potential vis-à-vis industrial protein purification. Overall, a polymer - salt (citrates in particular) ATPS with an added inert supplementary salt can be regarded as a better option for purifying proteins.

Discovery of Food-Derived Dipeptidyl Peptidase IV Inhibitory Peptides: A Review.

Diabetes is a chronic metabolic disorder which leads to high blood sugar levels over a prolonged period. Type 2 diabetes mellitus (T2DM) is the most common form of diabetes and results from the body's ineffective use of insulin. Over ten dipeptidyl peptidase IV (DPP-IV) inhibitory drugs have been developed and marketed around the world in the past decade. However, owing to the reported adverse effects of the synthetic DPP-IV inhibitors, attempts have been made to find DPP-IV inhibitors from natural sources. Food-derived components, such as protein hydrolysates (peptides), have been suggested as potential DPP-IV inhibitors which can help manage blood glucose levels. This review focuses on the methods of discovery of food-derived DPP-IV inhibitory peptides, including fractionation and purification approaches, in silico analysis methods, in vivo studies, and the bioavailability of these food-derived peptides. Moreover, food-derived DPP-IV inhibitory peptides discovered during this decade are listed and distributed in a 3D scatter plot graph based on their IC50, molecular weight, and grand average of hydropathicity values, which can help us to understand the relationship between the features of the peptides and their activities.

Protein⁻Phenolic Interactions as a Factor Affecting the Physicochemical Properties of White Bean Proteins.

This study was conducted with an aim to determine the interactions of pure phenolic compounds (gallic acid, ferulic acid, chlorogenic acid, quercetin, apigenin, and catechin) and phenolics from plant extracts (green tea and green coffee) with protein fractions of white bean (albumins and globulins). The physicochemical properties of complexes were established through an analysis of the UV-Vis spectrum; relative content of free amino groups, thiol groups, and tryptophan residues; chromatographic (SE-HPLC) and electrophoretic (SD-PAGE, Native-PAGE) properties; and conformational changes reflected by Fourier transform infrared spectra. Further, the effect of pH and ionic strength on the solubility and stability of complexes as well as the binding capacity of phenolics to proteins were determined. Results show that, in most cases, phenolics significantly affected the measured parameters; however, the effects were strongly differentiated by the type of phenolic compounds and protein fraction that were applied. Moreover, it may be that changes in the properties of complexes are reflected in the biological nature of proteins and phenolic compounds such as their bioavailability and physiological activity. However, due to the structural complexity of proteins, and the multitudinous factors that affect their interactions, such studies are a great and long-term challenge for the domain of food science.

[Enzymatic hydrolysates of food proteins for specialized foods for therapeutic and prophylactic nutrition].

The review considers some issues of obtaining, as well as physic-chemical, organoleptic, immunochemical (residual antigenicity) characteristics of enzymatic hydrolysates from food proteins (EHFP) that are widely used in food products for various purposes, as well as assessing their biological activity. The results of experimental works and patents, which describe the most widely used approaches to the production of EHFP with desired properties (hydrolysates for therapeutic and prophylactic products), as well as assessments of biological activity and immunochemical properties are given. The use of various enzyme preparations (of bacterial, fungal and animal origin), as well as one- and two-stage hydrolysis schemes and options for instrumentation of fermentolysis processes are considered. It is concluded that in order to achieve the required reduction in antigenicity for hydrolysates used as part of therapeutic (hypoallergenic) foods (to values not higher than 10-5 relative to the antigenicity of the original protein) membrane ultrafiltration stages are necessary. The main disadvantage of such hydrolysates is their unsatisfactory organoleptic properties (bitterness and high osmolarity) that can be improved using a number of additional technological approaches. The use of partial hydrolysates (or hydrolysates with an average degree of hydrolysis, with a residual antigenicity of 10-4 to 10-5) with significantly better organoleptic properties compared with deep hydrolysates in therapeutic foods is considered. Of considerable interest are the issues of immunomodulatory, antioxidant and hypoallergenic properties of EHFP. It has been suggested that soybean and chicken egg hydrolysates may be promising as functional ingredients with antimicrobial, antihypertensive and immunomodulatory effects in various specialized foods, as well as in cases of food intolerance only to cow milk proteins.

Prospects in the use of aptamers for characterizing the structure and stability of bioactive proteins and peptides in food.

Food-derived bioactive proteins and peptides have gained acceptance among researchers, food manufacturers and consumers as health-enhancing functional food components that also serve as natural alternatives for disease prevention and/or management. Bioactivity in food proteins and peptides is determined by their conformations and binding characteristics, which in turn depend on their primary and secondary structures. To maintain their bioactivities, the molecular integrity of bioactive peptides must remain intact, and this warrants the study of peptide form and structure, ideally with robust, highly specific and sensitive techniques. Short single-stranded nucleic acids (i.e. aptamers) are known to have high affinity for cognate targets such as proteins and peptides. Aptamers can be produced cost-effectively and chemically derivatized to increase their stability and shelf life. Their improved binding characteristics and minimal modification of the target molecular signature suggests their suitability for real-time detection of conformational changes in both proteins and peptides. This review discusses the developmental progress of systematic evolution of ligands by exponential enrichment (SELEX), an iterative technology for generating cost-effective aptamers with low dissociation constants (K d) for monitoring the form and structure of bioactive proteins and peptides. The review also presents case studies of this technique in monitoring the structural stability of bioactive peptide formulations to encourage applications in functional foods. The challenges and potential of aptamers in this research field are also discussed. Graphical abstract Advancing bioactive proteins and peptide functionality via aptameric ligands.

Peptides Derived from Foods as Supportive Diet Components in the Prevention of Metabolic Syndrome.

Metabolic syndrome (MSyn) includes physiological, biochemical, clinical, and metabolic abnormalities, leading to an increase in health problems like obesity, dyslipidemia, cardiovascular diseases, and diabetes, which contribute to an increase in mortality rate. One of the main factors having a key impact on our health is the food we consume. Thus, scientists work towards the discovery of novel bioactive compounds with therapeutic potential to address MSyn. According to scientific reports, peptides derived from food proteins exhibit bioactivities important for the prevention of MSyn diseases; that is, they regulate blood pressure and glycemia; reduce cholesterol level and body mass; and scavenge free radicals. The aim of this review is to study the potential role of peptides in the prevention of MSyn. Particularly peptides which exhibit the following activities: antihypertensive [angiotensin-converting enzyme (ACE) inhibition (EC 3.4.15.1)], antidiabetic [dipeptidyl peptidase IV (DPP-IV) (EC 3.4.14.5)/α-glucosidase (EC 3.2.1.20)/α-amylase (EC 3.2.1.1) inhibition)], cholesterol level reduction, antioxidative, and obesity prevention, were studied. If possible, special attention is paid in the review to the bioactivities of peptides that were measured in vivo. Some examples of peptides showing dual or multiple action against MSyn targets are presented. Moreover, using the database of bioactive peptide sequences (BIOPEP) we made a list of peptides serving simultaneous functions in counteracting MSyn dysfunctions. Such an approach may simplify the discovery of MSyn preventive peptides, as well as highlight some of them as potent bioactive ingredients that may be incorporated into foods. Moreover, the research strategy involving the in silico and in vitro/in vivo methodologies may be useful in the production of food protein hydrolysates supporting the treatment of MSyn dysfunctions.

[Metabolic effects of egg white enzymatic hydrolyzates: prospects of use in persons with metabolic syndrome (short review)].

The metabolic syndrome (MS), which is characterized by significant prevalence, constant growth of patients' number and high rate of cardiovascular complications, is one of actual problems of modern medicine. A way for optimization of the dietary status of patients with MS is the use of specialized foods with optimized chemical composition in their complex treatment. These products allow to correct hyperglycemia, dyslipidemia and antioxidant status disorders. The publications of the last decade show high interest of scientists to the problem of use of enzymatic hydrolysates of food proteins in dietary preventive products for people with metabolic disorders. High biological value of chicken egg protein and its enzymatic hydrolysates define the prospects of their use in specialized foods aimed at correction and/or prevention of MS clinical implications. The hydrolysis of chicken egg protein leads to the formation of biologically active peptides with antioxidant, hypotensive, anticoagulant and some other effects. As functional food ingredient, the enzymatic hydrolysate of chicken egg protein has some advantages over native protein - higher water solubility, digestibility and absorption in gastrointestinal tract. The results of preclinical in vitro and in vivo studies on evaluation of hypolipidemic effects of chicken egg protein and its enzymatic hydrolysates are discussed in this review. The analysis of the presented publications shows, that introduction of chicken egg protein and its enzymatic hydrolysates into the diet of animals with induced metabolic syndrome had hypolipidemic and antihypertensive effects. The main mechanisms of hypolipidemic action of protein hydrolysates and peptides in gastrointestinal tract are briefly discussed in this review. The prospects of the production of enzymatic hydrolysates of chicken egg protein with defined hypolipidemic properties for their inclusion into dietary products for prevention and treatment of MS are proved in the review.

Food Protein Based Core-Shell Nanocarriers for Oral Drug Delivery: Effect of Shell Composition on in Vitro and in Vivo Functional Performance of Zein Nanocarriers.

The study was aimed at systematically investigating the influence of shell composition on the particle size, stability, release, cell uptake, permeability, and in vivo gastrointestinal distribution of food protein based nanocarriers for oral delivery applications. Three different core-shell nanocarriers were prepared using food-grade biopolymers including zein-casein (ZC) nanoparticles, zein-lactoferrin (ZLF), nanoparticles and zein-PEG (ZPEG) micelles. Nile red was used as a model hydrophobic dye for in vitro studies. The nanocarriers had negative, positive, and neutral charge, respectively. All three nanocarriers had a particle size of less than 200 nm and a low polydispersity index. The nanoparticles were stable at gastrointestinal pH (2-9) and ionic strength (10-200 mM). The nanocarriers sustained the release of Nile red in simulated gastric and intestinal fluids. ZC nanoparticles showed the slowest release followed by ZLF nanoparticles and ZPEG micelles. The nanocarriers were taken up by endocytosis in Caco-2 cells. ZPEG micelles showed the highest cell uptake and transepithelial permeability followed by ZLF and ZC nanoparticles. ZPEG micelles also showed P-gp inhibitory activity. All three nanocarriers showed bioadhesive properties. Cy 5.5, a near IR dye, was used to study the in vivo biodistribution of the nanocarriers. The nanocarriers showed longer retention in the rat gastrointestinal tract compared to the free dye. Among the three formulations, ZC nanoparticles was retained the longest in the rat gastrointestinal tract (≥24 h). Overall, the outcomes from this study demonstrate the structure-function relationship of core-shell protein nanocarriers. The findings from this study can be used to develop food protein based oral drug delivery systems with specific functional attributes.

Food-derived immunomodulatory peptides.

Food proteins contain specific amino acid sequences within their structures that may positively impact bodily functions and have multiple immunomodulatory effects. The functional properties of these specific sequences, also referred to as bioactive peptides, are revealed only after the degradation of native proteins during digestion processes. Currently, milk proteins have been the most explored source of bioactive peptides, which presents an interesting opportunity for the dairy industry. However, plant- and animal-derived proteins have also been shown to be important sources of bioactive peptides. This review summarizes the in vitro and in vivo evidence of the role of various food proteins as sources of immunomodulatory peptides and discusses the possible pathways involving these properties. © 2016 Society of Chemical Industry.