Use of the guanidination reaction for determining reactive lysine, bioavailable lysine and gut endogenous lysine
- 411 Downloads
Determining the bioavailability of lysine in foods and feedstuffs is important since lysine is often the first limiting indispensable amino acid in diets for intensively farmed livestock (pigs and poultry) and also in many cereal-based diets consumed by humans. When foods or feedstuffs are heat processed, lysine can undergo Maillard reactions to produce nutritionally unavailable products. The guanidination reaction, the reaction of O-methylisourea with the side chain amino group of lysine that produces homoarginine, has been used to determine the unmodified lysine (reactive lysine) in processed foods and feedstuffs and also true ileal digestible reactive lysine (bioavailable lysine). The advantages of the guanidination method in comparison with other reactive lysine methods such as the fluorodinitrobenzene, trinitrobenzenesulphonic acid and dye-binding methods are that it is very specific for reactive lysine and also that the method is relatively straightforward to conduct. The specificity of the guanidination reaction for the lysine side chain amino group is particularly important, since ileal digesta will contain N-terminal groups in the form of free amino acids and peptides. The main disadvantage is that complete conversion of lysine to homoarginine is required, yet it is not straightforward to test for complete guanidination in processed foods and feedstuffs. Another disadvantage is that the guanidination reaction conditions may vary for different food types and sometimes within the same food type. Consequently, food-specific guanidination reaction conditions may be required and more work is needed to optimise the reaction conditions across different foods and feedstuffs.
KeywordsHomoarginine Lysine Guanidination Reactive Bioavailable
Conflict of interest
The author declares that there is no conflict of interest.
- Eklund M, Caine WR, Sauer WC, Huang GS, Diebold G, Schollenberger M, Mesenthin R (2013) Guanidination procedures increases standardised ileal digestibilities of nitrogen and amino acids in rapeseed meal, soybean meal and peas fed to growing pigs. Anim Prod Sci 53:265–273Google Scholar
- Finot PA, Bujard E, Mottu F, Mauron J (1977) Availability of the true Schiff’s bases of lysine. Chemical evaluation of the Schiff’s base between lysine and lactose in milk. In: Friedman M (ed) Protein crosslinking-B: nutritional and medical consequences. Plenum, New York, pp 343–366CrossRefGoogle Scholar
- Fontaine J, Zimmer U, Moughan PJ, Rutherfurd SM (2007) Effect of heat damage in an autoclave on the reactive lysine contents of soy products and corn distillers dried grains with solubles. Use of the results to check on lysine damage in common qualities of these ingredients. J Agric Food Chem 55:10737–10743CrossRefPubMedGoogle Scholar
- Krause R, Knoll K, Henle T (2003) Studies on the formation of furosine and pyridosine during acid hydrolysis of different Amadori products of lysine. Eur Food Res Technol 216:277–283Google Scholar
- Moughan PJ (2003) AA digestibility and availability in food and feedstuffs. In: Ball RO (ed) Digestive physiology in pigs. Proc. 9th Intl. Symp. Univ. Alberta, Alberta, Canada, pp 199–221Google Scholar
- Nyachoti CM, McNeilage-Van de Wiele EM, de Lange CF, Gabert VM (2002) Evaluation of the homoarginine technique for measuring true ileal amino acid digestibilities in pigs fed a barley-canola meal-based diet. J Anim Sci 802:440–448Google Scholar
- Pahm AA (2008) Utilization of amino acids in corn distillers dried grains with solubles (DDGS) by pigs and poultry and the use of reactive lysine procedures to evaluate DDGS quality. Ph.D. dissertation, University of IllinoisGoogle Scholar
- Rutherfurd SM, Gilani GS (2009) Amino Acid Analysis. Curr Protoc Protein Sci 58:11.9.1–11.9.37Google Scholar
- Rutherfurd SM, Fanning AC, Miller BJ, Moughan PJ (2015) Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. J Nutr (In Press)Google Scholar