Nutritional and Functional Importance of Intestinal Sulfur Amino Acid Metabolism

Abstract

The metabolism of sulfur amino acids, methionine and cysteine, has been linked to several key aspects of human health and cellular function. In addition, the metabolism of dietary amino acids by the gastrointestinal tract is nutritionally important for normal function. In the case of sulfur amino acids (SAAs), in vivo, stable isotope studies in adults suggest that the splanchnic tissues utilize as much as 30-44% of the dietary methionine and cysteine. Similarly, the dietary methionine requirement is 30% lower in total parenteral nutrition (TPN)-fed piglets, a condition in which dietary nutrients largely bypass intestinal metabolism. These data suggest that intestinal metabolism of methionine is substantial, yet the intestinal metabolic fate of dietary methionine is largely unknown. Dietary cysteine likely plays a key role in intestinal epithelial antioxidant function as a precursor for glutathione. Moreover, cysteine and glutathione may also regulate epithelial cell proliferation via modulation of redox status. Recent evidence indicates that transformed colonic epithelial cells are capable of methionine transmethylation and transsulfuration. This review discusses the evidence of intestinal SAA metabolism and how this affects nutrient requirements and epithelial function.

Dietary starch sources affect net portal appearance of amino acids and glucose in growing pigs

“…Emerging evidence shows that the small intestine, a highly differentiated and complex organ, is not only responsible for the terminal digestion and absorption of protein but also plays an important role in amino acid metabolism (Stoll et al, 1998;Wu, 1998;Shoveller et al, 2005). Almost all of glutamate and aspartate in the diet are catabolized by the small intestinal mucosa in the first pass (Burrin et al, 2000).…”

“…Almost all of glutamate and aspartate in the diet are catabolized by the small intestinal mucosa in the first pass (Burrin et al, 2000). The small intestinal mucosa also degrades enteral Gln, Arg, Pro, branched-chain amino acids (BCAA) and Lys, and perhaps enteral Met, Phe, Thr, Gly and Ser, such that 30% to 50% of these dietary amino acids do not enter the portal circulation (Stoll et al, 1998;Wu, 1998;Shoveller et al, 2005). Because dietary amino acids are major fuels for the small intestinal mucosa, and are essential precursors for the intestinal synthesis of proteins, glutathione, polyamines, nitric oxide, purine and pyrimidine nucleotides, intestinal amino acid metabolism is obligatory for maintaining intestinal mucosal mass, function and integrity (Wu et al, 2005).…”

The effects of dietary whey protein concentrate level on performance, selected intestinal tract and blood parameters, and thiobarbituric acid reactive substances in the liver and breast meat of broiler chickens

“…WP belongs to a class of proteins with an exceptionally high biological value and very rich in lysine and leucine, with considerable contents of methionine plus cystine. The last two play a key role in cellular antioxidant status, serving as precursors for glutathione (Shoveller et al, 2005). In addition to their excellent nutritional value, WP possesses health-related properties with regard to immune enhancing effects, gastrointestinal hormone secretion, antimicrobial and antiviral actions, and such other metabolic functions as satiety response and muscle anabolism (Madureira et al, 2007).…”

Homocysteine and Polyamines: Metabolic Relationship and Its Clinical Significance in Folate Inhibitors Chemotherapy

“…Гомоцистеин может превратиться в цистеин через цистатионин по пути необратимого транс-сульфирования [39]. Гомоцистеин может также реметилироваться обратно в метионин (см.…”

“…Ферменты, участвующие в этих превращениях, -спермидинсинтаза и спермин-синтаза [1,26]. В отличие от большого количества сообщений о влиянии гомоцистеина на путь кле-точного метилирования за счет изменения уровней SAM [39,42] существует недостаток информации о его влиянии на синтез полиаминов, хотя теорети-чески гомоцистеин может повлиять на эти пути. Внутриклеточные спермин и спермидин разлага-ются спермидин/спермин N1-ацетилтрансферазой (ССАТ) и N1-ацетилполиаминоксидазой (АПАО).…”