Study of spontaneous deamidation of camel's milk α-lactalbumin

International audienceMany proteins are susceptible, both in vivo and in vitro, to non enzymatic deamidation that can lead to alterations in their structure and biological functions. Aspartyl and isoaspartyl residues are the primary products of this non-enzymatic reaction that proceeds through the succinimide pathway with a metastable cyclic imide as an intermediate. Camel's milk α-lactalbumin was purified by FPLC on ion exchange column (Mono Q) and the pure fraction of the α-lactalbumin was dialysed and freeze-dried. Purified α-lactalbumin was incubated for 80h at 37°C in deamidation buffer (150 mM phosphate buffer, pH 7.4 or 8.4). Protein concentration was 15 mg mL-1. At specific time points, 150 µL aliquots were withdrawn and the kinetics of spontaneous deamidation of the α-lactalbumin was followed by FPLC which shows the presence of two isoformes, this result was confirmed by electrophoresis analysis on Alkaline-PAGE. The pHi of the two isoformes was estimated by a two-dimensional isoelectrophoresis. To compare the rate of camel α-lactalbumin deamidation, the half-life of native α-lactalbumin was calculated at pH 7.4 and 8.4, the result shows that the deamidation of camel α-lactalbumin is faster at elevated pH

Nutritional and Hygienic Quality of Raw Milk in the Mid-Northern Region of Algeria: Correlations and Risk Factors

This paper aims to study the overall quality of raw milk in the mid-northern region of Algeria. The analysis results showed a decrease in the average temperature for the delivery of 1,54°C with P<0.001. However, no significant variation (P>0.05) was observed in almost all the physical and nutritional parameters studied (pH, fat content, and protein content) between M1 and M2. The average contamination by total mesophilic aerobic bacteria (TMAB), coliforms, yeasts, molds, and different pathogens in samples taken at M1 showed significant changes at M2. This was confirmed by the decrease of reduction time of methylene blue (RTMB), about 54%. The variation was described as follows: (P>0.05) for yeasts and (P<0.05) for molds in M1 and M2, (P<0.05) for TMAB in M1, and (P<0.001) for TC, FC, and TMAB in M2. The analysis for the detection of Salmonella spp. showed no contamination in all samples tested, while antibiotic residues were detected in 35% of milks delivered. In conclusion, several risk factors have been identified in this study, namely, the effect of the season and the distance between the farm and the dairy unit

Free fatty acid profiles and cholesterol and lipid indexes of raw ewe's milk from two Algerian breeds (Ouled-Djellal and Rumbi), collected in the steppe area

Description of the subject. This article aims to characterize the fat content of raw ewe's milk, collected locally in the Algerian central steppe, an area highly appreciated for its production of smen (traditional butter). Objectives. The objective of this study was to investigate the free fatty acid profile and the cholesterol and lipid indexes of raw ewe's milk from two Algerian local breeds (Ouled-Djellal and Rumbi). Method. Milk was collected from 20 ewes of each breed three times during the middle stage of lactation. The milk fat was extracted using the Rose-Gottlieb method. Fatty acids were analyzed by gas chromatography. Results. Palmitic (24.4% +/- 3.3), oleic (24.2% +/- 4.6), stearic (10.8% +/- 3.5), myristic (10.4% +/- 1.9) and capric (8.3% +/- 3.5) acids dominated and accounted for 78.1% of the total fatty acids. Saturated fatty acids predominated compared to unsaturated fatty acids (69.6% +/- 5.3 vs 30.8% +/- 5.1), and monounsaturated fatty acids outweighed the polyunsaturated (26.3% +/- 4.7 vs 4.5% +/- 1.1). The Ouled-Djellal milk had a higher short-chain fatty acid content than the Rumbi milk (p < 0.05). On the other hand, the Rumbi milk was richer in medium chain fatty acids. The two types of milk differed significantly regarding their palmitic and palmitoleic acid content (p < 0.05). Within the long chain of fatty acids, only the stearic acid (10.88% +/- 2.83 vs 12.34% +/- 2.75; p < 0.01) and the arachidic acid (0.26% +/- 0.18 vs 0.35% +/- 0.09; p < 0.05) were influenced by the breed. Conclusions. Results showed that milk from the Rumbi ewe was richer in fatty acids than the milk from the Ouled-Djellal and that Rumbi ewe's milk may be of value in dairy technology due to the socio-economic impact that it can generate

Effect of nonenzymatic deamidation on the structure stability of Camelus dromedarius α-lactalbumin

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Extraction of Polyphenols from Olive Leaves Employing Deep Eutectic Solvents: The Application of Chemometrics to a Quantitative Study on Antioxidant Compounds

The extraction of phenolic compounds from olive leaves was optimized using three glycerol-based deep eutectic solvents (DESs) with lysine, proline, and arginine. A three-level Box–Behnken design was used to examine the influence of the liquid/solid ratio, concentration of DESs, and extraction temperature on the yield of the extraction process. A second-order polynomial model was used for predicting the polyphenol extraction yield. The optimal predicted conditions were used for extractions and they provided the highest total phenol yields with the glycerol–lysine exhibiting the best performance. Quantification of tyrosol, hydroxytyrosol, oleuropein, luteolin-7-O-glucoside, and rutin in the extracts showed high content in tyrosol in all DESs, particularly with glycerol–lysine and relatively similar contents with other studies for the other phenolic compounds. Finally, a linear relationship between tyrosol content and the total phenolic content of the extracts was observed

Dromedary camel milk proteins, a source of peptides having biological activities – A review

Many useful properties are assigned to camel (Camelus dromedarius) milk, which is traditionally used for the treatment of tuberculosis, gastroenteritis, and allergy in many countries. Some amino acid sequences, which are encrypted in the camel proteins, may play a beneficial role in human health once they are released from milk either in vivo during normal digestion or by proteolysis with purified enzymes or during bacterial fermentation. Similar to the bovine milk counterparts, camel milk bioactive peptides may display a variety of potential activities that were almost always unveiled from in vitro analyses: antimicrobial, anti-oxidative, anti-hypertensive, anti-inflammatory, and immunomodulatory activities. Today, there is a growing interest for bioactive peptides generated from camel milk. This paper reviews available data on the potential biological activities of the camel milk proteins and their peptides liberated either during milk fermentation with proteolytic bacterial strains or by enzyme hydrolysis with specific proteases or simulated gastro-intestinal digestion

Extraction of Polyphenols from Olive Leaves Employing Deep Eutectic Solvents: The Application of Chemometrics to a Quantitative Study on Antioxidant Compounds

The extraction of phenolic compounds from olive leaves was optimized using three glycerol-based deep eutectic solvents (DESs) with lysine, proline, and arginine. A three-level Box&ndash;Behnken design was used to examine the influence of the liquid/solid ratio, concentration of DESs, and extraction temperature on the yield of the extraction process. A second-order polynomial model was used for predicting the polyphenol extraction yield. The optimal predicted conditions were used for extractions and they provided the highest total phenol yields with the glycerol&ndash;lysine exhibiting the best performance. Quantification of tyrosol, hydroxytyrosol, oleuropein, luteolin-7-O-glucoside, and rutin in the extracts showed high content in tyrosol in all DESs, particularly with glycerol&ndash;lysine and relatively similar contents with other studies for the other phenolic compounds. Finally, a linear relationship between tyrosol content and the total phenolic content of the extracts was observed

Identification by FT-ICR-MS of Camelus dromedarius α-lactalbumin variants as the result of nonenzymatic deamidation of Asn-16 and Asn-45

International audienceNonenzymatic deamidation of asparaginyl residues can occur spontaneously under physiological conditions principally when a glycyl residue is at the carboxyl side of Asn and leads to formation of aspartyl and isoaspartyl residues. This modification can change the biological activity of proteins or peptides and trigger an auto-immune response. The α-lactalbumins of members of the Camelidae family are the only of described α-lactalbumins that carry two AsnGly sequences. In the present study, high-resolution mass spectrometry, which enables accurate mass measurement has shown that Asn16 and Asn45 underwent a nonenzymatic deamidation, the sequence Asn45–Gly46 being deamidated spontaneously at near-neutral and basic pH and Asn16–Gly17 rather at basic pH. The 16–17 sequence was probably stabilized at near-neutral pH by hydrogen bonds according to the molecular modelisation performed with the camel protein