Amino acids response patterns

Under normal feeding patterns the rate of tissue protein catabolism is more or less constant throughout the day it is only in cachexia that there is an increased rate of protein catabolism. There is net protein catabolism in the postabsorptive phase of the feeding cycle and net protein synthesis in the absorptive phase, when the rate of synthesis increases by about 20-25%. The increased rate of protein synthesis is, again, a response to insulin action. Protein synthesis is an energy-expensive process, accounting for up to almost 20% of energy expenditure in the fed state, when there is an ample supply of amino acids from the diet, but under 9% in the starved state. 

Figure 9(a) shows the response patterns to typical amino acids, each of which elicits different taste quality in humans [23]. Each channel responded to them in different ways depending on their tastes. L-Tryptophan, which elicits almost pure bitter taste, increased the potentials of channels 1, 2 and 3 greatly. This tendency was also observed for other amino acids which mainly exhibit bitter taste L-phenylalanine and L-isoleucine. L-Valine and L-methionine, which taste mainly bitter and slightly sweet, decreased the potential of channel 5 the responses of channels 1 and 2 were small. 

On the other hand, L-alanine, glycine and L-threonine taste mainly sweet [26]. Only for these amino acids, the potentials of channels 1 and 2 decreased. L-Glutamic acid and L-histidine monohydrochloride, which taste mainly sour, increased each of the potentials of channels 1-5 to almost the same degree. Only monosodium L-aspartate elicits mainly umami taste in humans among amino acids used here the response pattern was different from those of the other amino acids. 

Figure 9. (a) Response patterns for several amino acids. Symbols , O, , and denote L-glutamic acid, L-tryptophan, monosodium L-aspartate monohydrate, L-valine and L-alanine, respectively, (b) Scattering diagram of amino acids on PCI and PC2. 

Folmer-Andersen, J. F., Kitamura, M., Anslyn, E. V., Pattern-based discrimination of enantiomeric and structurally similar amino acids An optical mimic of the mammalian taste response. J. Am. Chem. Soc. 2006,128, 5652-5653. 

Kochakian was the first to demonstrate the effects of androgens of the liver, not only in terms of size and morphology, but also with respect to enzymic composition fumarase, catalase and D-amino acid oxidase activities were particularly sensitive to androgenic manipulation [32]. Subsequent studies confirmed and extended our understanding of the androgenic responses in liver, but illustrated that they were subject to extreme species variation. No common pattern of hepatic responses to androgens has emerged. 

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