Prevention of amino acid racemization during guanidination — a prerequisite for measurement of protein digestibility by homoarginine labeling

Vrese, Michael de; Middendorf, K.; Hagemeister, H.

doi:10.1007/bf01614436

Cited by 10 publications

(6 citation statements)

References 8 publications

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“…The current study and others (Maga, 1981;de Vrese et al, 1995;Imbeah et al, 1996) show that the extent of guanidination is higher in animal proteins than in plant proteins. Reasons for this are not obvious.…”

Section: Rates Of Lysine Conversion Into Homoargininesupporting

confidence: 67%

“…(particularly with regard to increasing MIU concentration) should be done with caution as this may interfere with the availability of some nutrients in treated samples (de Vrese et al, 1995). Also, due to a high variability in guanidination rates within ingredients across various studies, continued investigations into the conditions that influence guanidination are warranted.…”

Section: Rates Of Lysine Conversion Into Homoargininementioning

confidence: 99%

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Evaluation of the homoarginine technique for measuring true ileal amino acid digestibilities in pigs fed a barley-canola meal-based diet

Nyachoti

Wiele

Lange

et al. 2002

Journal of Animal Science

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The homoarginine technique has been suggested as a means to determine true ileal amino acid digestibilities in nonruminant animals fed protein-containing diets. Conditions for guanidinating lysine to homoarginine in barley and canola meal and the effect of this process on nutrient composition and ileal digestibilities in the resulting material were investigated. Conditions tested were methylisourea concentration (0.4, 0.5, or 0.6 M) and reaction time (4 or 6 d) at pH 10.5. Using 0.4 methylisourea M solution for 4 or 6 d gave guanidination rates of 72.5 and 78.5% for barley and 72.3 and 75.2% for canola meal, respectively. Using 0.5 M gave 88.0 and 84.6% guanidination rates in barley and canola meal, respectively, after a 6-d reaction time. Under these conditions, guanidination did not change the nutrient composition of barley (P > 0.10), whereas it increased CP (38.4 vs 49.0%), crude fiber (10.2 vs 16.0%), acid detergent fiber (30.0 vs 43.4%) and neutral detergent fiber (29.8 vs 49.4%) levels in canola meal (P < 0.05). Four 33.6-kg barrows fitted with a simple T-cannula at the terminal ileum were fed a 16% CP unguanidinated barley and canola meal-based diet for four consecutive 14-d periods. Ileal digesta were collected continuously for 24 h on d 12 and 14 to determine apparent nutrient digestibilities. On the morning of d 14, pigs were fed a diet in which half of the barley and canola meal was replaced with guanidinated material for determining true ileal amino acid digestibilities. Digesta samples were pooled by pig and by 24-h period to give 16 observations per diet. Apparent ileal digestibilities of DM, CP, and AA in the unguanidinated and guanidinated barley-canola meal diet were similar (P > 0.10) despite the changes observed in canola meal. Apparent ileal lysine digestibility was 73.9 and 74.5% in the unguanidinated and guanidinated diet, respectively. The true ileal lysine digestibility was 88.1%. The present results show that guanidination does not interfere with digestion and further support the use of the homoarginine method for determining true ileal amino acid digestibilities in pigs fed practical diets. A methylisourea solution of 0.5 M and a 6-d reaction time are recommended for converting lysine to homoarginine in barley and canola meal.

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Section: Rates Of Lysine Conversion Into Homoargininesupporting

confidence: 67%

Section: Rates Of Lysine Conversion Into Homoargininementioning

confidence: 99%

Evaluation of the homoarginine technique for measuring true ileal amino acid digestibilities in pigs fed a barley-canola meal-based diet

Nyachoti

Wiele

Lange

et al. 2002

Journal of Animal Science

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“…However, if HA is rapidly hydrolyzed by arginase in the liver to lysine and urea and HA serves as an effective source of lysine to the animal, then this concern is unjustified. The fact that optimum guanidination conditions may vary for individual proteins and that near complete guanidination is not always achieved may impose some limitations on this method (Maga 1981;Rutherfurd and Moughan 1990;de Vrese et al 1994). So far this method has largely been used with diets having just one, purified protein source.…”

Section: Ii43 Homoarginine Techniquementioning

confidence: 99%

Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review

Nyachoti¹,

Lange²,

McBride³

et al. 1997

Can. J. Anim. Sci.

236

163

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Nyachoti, C. M., de Lange, C. F. M., McBride, B. W. and Schulze, H. 1997. Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review. Can. J. Anim. Sci. 77: 149-163. During the past two decades endogenous gut N losses (ENL) at the distal ileum in the growing pig have received considerable attention in swine nutrition research. Estimates of ENL are important for determining true ileal N and amino acid digestibilities and for identifying means to improve the efficiency of N and energy utilization in growing pigs. Endogenous secretions originate from various sources including saliva, pancreatic secretions, bile, sloughed off epithelial cells, serum albumin and mucin. It has been estimated that 70 to 80% of endogenous N secretions are digested and re-absorbed. Therefore, ENL represents only a fraction of total endogenous N secreted into the gut. Increased ENL are likely associated with elevated rates of gut protein synthesis. This is bound to increase maintenance energy and amino acid requirements of pigs. Traditionally, ENL were determined by feeding protein-free diets or by the regression method. Various alternative techniques ( 15 N-isotope dilution technique, homoarginine technique, enzymatically hydrolysed casein method) are now available to estimate the ENL in pigs fed protein-containing diets. Each of these techniques has some limitations and all require different assumptions. Results obtained with these alternative techniques indicate that the net ENL losses are much higher and more variable than previously estimated, and that they are affected both by animal and dietary factors. Recent estimates of ENL losses vary between 1.8 and 8.3 g kg -1 dry matter intake. The main factors (feed intake, body weight, content of anti-nutritional factors, fibres and [digestible] protein) that affect ENL and approaches (plant breeding and selection, ingredient processing and use of exogenous enzymes) to reduce ENL are discussed in this review. In addition, the metabolic costs associated with ENL are estimated.

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“…Using the optimized reaction conditions as mentioned above, we attempted FTDR-based macrocyclization on these peptides with aliphatic dithiols of various lengths or more rigid and reactive benzenedimethanethiol linkers. The reaction mixtures had a final pH of 9.0-9.5, which together with the mild reaction temperature (37 °C) should lead to minimal epimerization 52,53 . As demonstrated in Fig.…”

Section: Resultsmentioning

confidence: 99%

Unprotected peptide macrocyclization and stapling via a fluorine-thiol displacement reaction

et al. 2022

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We report the discovery of a facile peptide macrocyclization and stapling strategy based on a fluorine thiol displacement reaction (FTDR), which renders a class of peptide analogues with enhanced stability, affinity, cellular uptake, and inhibition of cancer cells. This approach enabled selective modification of the orthogonal fluoroacetamide side chains in unprotected peptides in the presence of intrinsic cysteines. The identified benzenedimethanethiol linker greatly promoted the alpha helicity of a variety of peptide substrates, as corroborated by molecular dynamics simulations. The cellular uptake of benzenedimethanethiol stapled peptides appeared to be universally enhanced compared to the classic ring-closing metathesis (RCM) stapled peptides. Pilot mechanism studies suggested that the uptake of FTDR-stapled peptides may involve multiple endocytosis pathways in a distinct pattern in comparison to peptides stapled by RCM. Consistent with the improved cell permeability, the FTDR-stapled lead Axin and p53 peptide analogues demonstrated enhanced inhibition of cancer cells over the RCM-stapled analogues and the unstapled peptides.

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Prevention of amino acid racemization during guanidination — a prerequisite for measurement of protein digestibility by homoarginine labeling

Cited by 10 publications

References 8 publications

Evaluation of the homoarginine technique for measuring true ileal amino acid digestibilities in pigs fed a barley-canola meal-based diet

Evaluation of the homoarginine technique for measuring true ileal amino acid digestibilities in pigs fed a barley-canola meal-based diet

Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review

Unprotected peptide macrocyclization and stapling via a fluorine-thiol displacement reaction

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