Characterization of Egg White Proteins

Nelson T.

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Characterization of Egg White Proteins

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Egg White Proteins, ovoinhibitor, ovoglycoprotein, flavoprotein, avidin and ovoglobuli

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Abstract

Egg white or albumin is the biggest fraction of whole egg and contains 88% water, 11% proteins, 0.2% fats and 0.2% minerals. The major constituent of egg white proteins are 60% of ovalbumin, 12% of conalbumin, 11% of ovomucoid, and 3.5% of lysozyme. It also contains small amount of ovoinhibitor, ovoglycoprotein, flavoprotein, avidin and ovoglobulins (Brown 2010).

Ovalbumin is the most abundant egg white protein with isoelectric point of 4.58. It has molecular weight of 44.5kDa (Coultate 2009). Ovalbumin is found to have antimicrobial effect, due to its ability to bind iron. This causes deprivation of irons essential for growth of microorganisms (Abdou et al. 2013). It is also suggested that the hydrophobicity and its positive charge contributes to ovalbumin's bactericidal actions against Gram-negative bacteria (Belitz et al. 2009). It also acts as a storage proteins and major nutrient source of amino acids for embryo in late developing stage (Mine & Yang 2008). In food industry, the amphilic behavior of ovalbumin makes it suitable to be used as foaming agent. It is used mainly as stabilizer in bakery products where their texture and structure have to be maintained during and after processing (Du et al. 2002). In medical field, ovalbumin is administered when there is suspected heavy metal poisoning to chelate the metal ions, preventing them to be further absorbed through digestive system.

Introduction
Methods and Materials
Isolation of lysozyme
Activity and Assay of Lysozyme
Iron binding Capacity of Conalbumin II
Conclusion

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[...] Lastly, centrifuging purifies the lysozyme fractions recovered and removes other proteins from solution Lysozyme D will be expected to contain highest concentration of purified lysozyme. Lysozyme A will contain all proteins present in egg white such as ovalbumin, conalbumin and lysozyme as no separation is done. Lysozyme B and C fractions will contain a number of mixed proteins in egg white except lysozyme, since most of the lysozyme has already been bound to the CM exchanger. Lysozyme D however contains purely only lysozyme without mixture of other protein fractions. [...]

[...] Undiluted fractions would have very high lysozyme activities. Amberlite IR 120 was a strong cation exchange resin that had negative charge. It would bind to positively charge iron (III) ions. Conalbumin consisted of two lobes linked by α-helix structure and each lobe could reversibly bind to iron (III) ions (Mine 2010). Bicarbonate ions further enhanced binding of conalbumin to iron ions. Theoretically one mole of conalbumin would bind to two moles of iron since conalbumin consisted of two metal ion binding sites (Belitz et al. [...]

[...] Du Prokop A & Tanner RD 2002, ‘Effect of Denaturation by Preheating on the Foam Fractionation Behavior of Ovalbumin, Journal of Colloid and Interface Science, vol pp. 487-492. Iqbal SA & Mido Y 2008, ‘Protein in Man's Diet', in Food Chemistry, 1st edn., Discovery Publishing House, New Delhi, pp. 8-38. Jiang CM, Wang MC, Chang WH & Chang HM 2001, ‘Isolation of Lysozyme from Hen Egg Albumin by Alcohol-Insoluble Cross-Linked Pea Pod Solid Ion- exchange chromatography', Journal of Food Science, vol no pp. 1089- 1092. Khan HU 2012, Role of Ion Exchange Chromatography in Purification and Characterization of Molecules', in Ion Exchange Technologies, InTech, Croatia, pp. [...]

[...] The remaining egg white was measured. (56mL) 56mL of saturated ammonium sulfate was slowly added to the remaining volume of egg white and the solution was stirred constantly for a well-mixed mixture. The solution was allowed to stand for 30 minutes with occasional stirring. The suspension was centrifuged at low speed of 3000 rpg for 15 minutes after that. The pellet was discarded. The supernatant was collected and the pH of the supernatant was retained to the pH 4.7 by adding 8.6 mL of 0.25 M sulfuric acid, H2SO4. [...]

[...] Wrolstad RE, Decker EA, Schwartz SJ & Sporns P 2005, ‘Proteins', in Handbook of Food Analytical Chemistry, Water, Proteins, Enzymes, Lipids and Carbohydrate, John Wilet and Sons Inc., USA, p Yamamoto Y & Ishihara T 1999, ‘Ion-exchange Chromatography of Proteins Near the Isoelectric Points', Journal of Chromatography vol pp. 31-36. The initial volume of egg white was measured and recorded. (60mL) 2mL of the egg white was transferred into two microfuge tube each. The microfuge tube was labelled and kept for analysis. [...]

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