Antihypertensive effect of angiotensin I-converting enzyme inhibitory peptides derived from hemoglobin

Bioactivities and ACE-inhibitory peptides releasing potential of lactic acid bacteria in fermented soy milk

Abstract

This study was designed to evaluate the bioactivities such as β-glucosidase activity, α-galactosidase activity, and the growth behavior of the Lactobacillus cultures in soy milk medium. Ten Lactobacillus cultures were considered in this study. L. fermentum (M2) and L. casei (NK9) were selected due to their better α-galactosidase, β-glucosidase activity and growth behavior in soy milk medium during fermentation. Further, soy milk fermented with M2 showed higher proteolytic activity (0.67 OD) and ACE-inhibitory (48.44%) than NK9 (proteolytic activity: 0.48 OD and ACE-inhibitory activity: 41.33%). Bioactive peptides produced during the fermentation of soy milk using the selected Lactobacillus cultures were also identified with potent ACE-inhibitory activity by MALDI-TOF spectrometry, and the identified ACE inhibitory peptide sequences from fermented soy milk were characterized using Biopep database.

Graphical abstract

Improvement of chicken plasma protein hydrolysate angiotensin I-converting enzyme inhibitory activity by optimizing plastein reaction

Chicken plasma protein hydrolysate (CPPH) was prepared by trypsin with angiotensin I-converting enzyme (ACE) inhibitory activity of 53.5% ± 0.14% and the degree of hydrolysis (DH) of 16.22% ± 0.21% at 1 mg·ml-1; then, five proteases, including pepsin, trypsin, papain, alcalase, and neutrase, were employed to improve ACE inhibitory ability by catalyzing plastein reaction. The results indicated that trypsin-catalyzed plastein reaction showed the highest ACE inhibitory activity. The exogenous amino acids of leucine, histidine, tyrosine, valine, and cysteine were selected to modify the CPPH. The leucine-modified plastein reaction released the highest ACE inhibitory activity. The effects of four reaction parameters on plastein reaction were studied, and the optimal conditions with the purpose of obtaining the most powerful ACE inhibitory peptides from modified products were obtained by response surface methodology (RSM). The maximum ACE inhibition rate of the modified hydrolysate reached 82.07% ± 0.03% prepared at concentration of hydrolysates of 30%, reaction time of 4.9 hr, pH value of 8.0, temperature of 40°C, and E/S ratio of 5,681.62 U·g-1. The results indicated that trypsin-catalyzed plastein reaction increased ACE inhibitory activity of chicken plasma protein hydrolysates by 28.57%.

New insights into meat by-product utilization

Meat industry generates large volumes of by-products like blood, bones, meat trimmings, skin, fatty tissues, horns, hoofs, feet, skull and viscera among others that are costly to be treated and disposed ecologically. These costs can be balanced through innovation to generate added value products that increase its profitability. Rendering results in feed ingredients for livestock, poultry and aquaculture as well as for pet foods. Energy valorization can be obtained through the thermochemical processing of meat and bone meal or the use of waste animal fats for the production of biodiesel. More recently, new applications have been reported like the production of polyhydroxyalkanoates as alternative to plastics produced from petroleum. Other interesting valorization strategies are based on the hydrolysis of by-products to obtain added value products like bioactive peptides with relevant physiological effects as antihypertensive, antioxidant, antidiabetic, antimicrobial, etc. with promising applications in the food, pharmaceutical and cosmetics industry. This paper reports and discusses the latest developments and trends in the use and valorisation of meat industry by-products.

WITHDRAWN: Bioactive peptides derived from meat proteins

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beta-Actin-derived peptides isolated from acidic extract of rat spleen suppress tumor cell growth

Twenty-two fragments of beta-actin and beta-actin-related protein were isolated from the acidic extracts of rat spleen tissue. beta-Actin fragments (75-90), (78-89), and (78-88), 0.01-1 microM, decreased live cell number of L929 murine tumor fibroblasts by 80-90%, with maximal cytotoxic effect of 30-40%. The fragments of (78-90) segment and the fragment of beta-actin-related protein (69-77) were less active (inhibitory effect up to 55%, cytotoxic-up to 25%).

The antihypertensive effect of peptides: a novel alternative to drugs?

Many types of bioactive peptides that inhibit angiotensin I, angiotensin I converting enzyme (ACE) and Ang II type 1 receptor (AT1) in the cardiovascular system contribute to the prevention and treatment of hypertension. These inhibitory peptides are derived from many food proteins or artificial synthetic products. Further research examining the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods. Our research also demonstrates that ACE inhibitory peptide LAP may lower blood pressure with no adverse effects.

Hemoglobin as a source of endogenous bioactive peptides: the concept of tissue-specific peptide pool

Scattered literature data on biologically active hemoglobin-derived peptides are collected in the form of tables. Respective structure-functional correlations are analyzed and the general conclusion is reached that hemoglobin fragments must have a profound physiological function. Evidence is presented that generation of hemoglobin fragments starts inside the erythrocytes. At that stage alpha- and beta-globin chains of hemoglobin predominantly give rise to relatively long peptides containing ca. 30 amino acid residues. The primary proteolysis is followed by the next degradation step coupled with excretion of newly formed shorter peptides form red blood cells. Both the primary and the secondary proteolysis products are subjected to further stepwise C- and N-terminal chain shortening, giving rise to families of closely related peptides that are actually found in animal tissue extracts. The possible sites of primary proteolysis are compared with the positions of the exposed secondary structure elements within the monomeric alpha- and beta-globins as well as the tetrameric hemoglobin. Two tentative schemes are proposed for hemoglobin degradation, one of which starts at the globin loops exposed on the surface of the tetramer and the other, at monomeric globins where more sites are available for the action of proteases. The concept of a "tissue-specific peptide pool" is formulated, describing a novel system of peptidergic regulation, complementary to the conventional hormonal and neuromodulatory systems. According to that description, hemoglobin is only a single example, although an important one, of a vast number of functional proteins providing their proteolytically derived fragments for maintaining the tissue homeostasis.

Fragments of functional proteins: role in endocrine regulation

Systematic analysis of structures, localization, formation and biological activities of endogenous peptides derived from functional proteins, such as hemoglobin, myelin basic protein, immunoglobulins, etc., allowed establishing the basic features of that group of compounds. The sets of these peptides in mammalian tissues, or "tissue-specific peptide pools" are: (i) tissue specific; (ii) stable at normal conditions; (iii) conservative in the same tissues of different mammalian species; (iv) dependent on the general state of homeostasis of tissue or the whole organism. Formation of such peptides has features of both conformation and site specificity and also involves the action of carboxy- and amino-peptidases. As a result, the families of structurally related families of peptides are generated. The fragments of functional proteins exhibit a wide range of the biological effects, characteristic both for hormones and parahormones, from hormone-releasing to growth-regulatory activity. At the same time, the molecular mechanisms of action of the majority of such peptides are unknown. On the basis of the data obtained the components of tissue-specific peptide pools are considered to form a novel regulatory system, complementary to other peptidergic systems such as hormonal, nervous, immune, etc. The biological role of the fragments of functional proteins in vivo and the patterns of interaction with other regulatory systems are suggested.