[Biologic availability and metabolic transit of amino acids modified by technological processing].

The biological availability of amino acids modified by industrial processes has been measured in trials on rats, and their metabolic transit (urinary and faecal excretions, transformation into CO2 and retention in organs) has been studied using molecules labelled with 14C. Maillard reaction products. epsilon-fructose-lysine is not utilized as lysine source. However, less than 10 p. 100 of this substance, bound to proteins, is excreted unmodified in the urine. Intestinal flora destroys most of the fraction which is not absorbed. Premelanoidins are partially absorbed and "burnt" in the organism, whereas high molecularightwe melanoïdins are totally excreted in the faeces. epsilon-(gamma-glutamyl)-lysine and epsilon-(beta-aspartyl)-lysine isopeptides. 80 to 100 p. 100 of free epsilon-(gamma-glutamyl)-lysine are utilized by the Rat. It seems to be absorbed by the intestine, and subsequently hydrolyzed by the kidney, thus releasing lysine. Utilization of this isopeptide bound to proteins has not been shown till now. Free epsilon-(beta-aspartyl)-lysine is not utilized as lysine source. Methionine sulfoxyde and methionine sulfone. Methionine sulfone is not utilized as methionine source whereas most of the free and bound methionine sulfoxide is, in part, it is "reduced" by the liver (perfused liver). Lysino-alanine. Formation of lysino-alanine reduces the availability of lysine and cystine. It is partially excreted in urines, mainly as free lysino-alanine, but also as acetylated derivatives and unknown catabolites.