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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.22, #1)
Cancer therapy and prevention by green tea: role of ornithine decarboxylase by U. Bachrach; Y.-C. Wang (pp. 1-13).
Green tea which is widely consumed in China, Japan and India, contains polyphenolic compounds, which account for 30% of the dry weight of the leaves. Most of the polyphenols are flavanols, of which (−)-epigallocatechin-3-gallate (EGCG) is most abundant. Epidemiological studies revealed that the incidences of stomach and prostate cancers are the lowest in the world among a population that consumes green tea on a regular basis. It has also been reported that the quantity of green tea consumed, plays an important role in reducing cancer risk and in delaying cancer outbreak and recurrence. Various systems were used to confirm anti-cancer activities of green tea and/or EGCG. These included experimental animals in which cancer was induced chemically. Cultured cells transformed chemically or by oncogenes were also used. These studies clearly demonstrated that green tea or EGCG have anticancer and cancer preventive properties. The mechanisms of these activities have also been studied in details. It has been shown that green tea and its active components interfere with signal transduction pathways. Thus the activities of various protein kinases are inhibited, the expression of nuclear proto-oncogenes declines and the activity of ornithine decarboxylase (ODC) is reduced. ODC, which catalyzes the rate-limiting step in the biosynthesis of polyamines is closely linked with cellular proliferation and carcinogenesis. Inhibitors of ODC, like α-difluoromethylornithine (DFMO) have long been used for cancer prevention and therapy. It has been suggested that polyamine depletion by green tea could offer one explanation for its anti-cancer activities.
Keywords: Keywords: Amino acids; Green tea; Polyphenols; (; )-Epigallocatechin-3-gallate (EGCG); Polyamines; Ornithine decarboxylase (ODC); Cancer prevention; Cancer therapy
Protein metabolism during an acute phase response in chickens by D. M. Barnes; Z. Song; K. C. Klasing; W. Bottje (pp. 15-26).
Fractional rates of liver, muscle, plasma and acute phase portein synthesis were measured in chickens injected with saline or E. coli lipopolysaccharide (LPS). Male Single Comb White Leghorns were infused with a primed constant infusion of 15N-L-methionine and 2H5-L-phenylalanine into the portal vein for 2 h. Changes in plasma amino acid enrichment were similar for both amino acids reaching an apparent plateau by the 30 min sampling time. The enrichment of plasma protein-bound amino acid was measurable after 1 h of isotope infusion and increased linearly over 2 h. LPS injection decreased free phenylalanine enrichment in the carotid artery (50%), and reduced tissue free methionine enrichment in the liver, pectoralis, and gastrocnemius by 16, 41, and 31% respectively. Isotopic enrichment of phenyl-alanine in liver protein, plasma protein and hemopexin increased in LPS injected birds relative to control birds. Fractional rates of muscle protein synthesis were not affected by LPS injection, however, liver protein, plasma protein, and hemopexin fractional synthesis rates increased 141, 161 and 266% respectively compared with untreated animals.
Keywords: Keywords: Amino acids; Acute phase response; Poultry; Stable isotopes; Hemopexin; Protein synthesis
Taurine modulates kallikrein activity and glucose metabolism in insulin resistant rats by A. T. Anitha Nandhini; C. V. Anuradha (pp. 27-38).
Taurine, a potent antioxidant has been reported to show an antidiabetic effect in streptozotocin-induced diabetes mellitus in which the development of hyperglycemia results from the damage to β cells of pancreas by reactive oxygen species. In addition, taurine also increases the excretion of nitrite and enhances the formation of kinins and would be expected to improve insulin resistance. The effect of taurine on insulin sensitivity was examined in the high fructose-fed rats, an animal model of insulin resistance. Male Wistar rats of body weight 170–190 g were divided into 4 groups: a control group and taurine-supplemented control group, taurine supplemented and unsupplemented fructose-fed group. An intravenous glucose tolerance test (IVGTT) and a steady state plasma glucose level (SSPG) were performed before the sacrifice. The fructose-fed rats displayed hyperglycemia and insulin resistance and they had a greater accumulation of glycogen than did control rats. Hyperglycemia and insulin resistance were significantly lower in the taurine supplemented fructose-fed group than in the unsupplemented fructose-fed group. Urinary kallikrein activity was higher in taurine-treated animals than in the rats fed only fructose. The activity of membrane bound ATPases were significantly lower in fructose-fed rats than in the control rats and were significantly higher in the taurine supplemented group than in the fructose-fed group. Taurine effectively improves glucose metabolism in fructose-fed rats presumably via improved insulin action and glucose tolerance.
Keywords: Keywords: Taurine; Insulin resistance; Glucose tolerance; Hepatic enzymes-membrane ATPases; Urinary kallikrein
Effects of arginine, L-alanyl-L-glutamine or taurine on neutrophil (PMN) free amino acid profiles and immune functions in vitro by J. Mühling; M. Fuchs; C. Fleck; A. Sablotzki; M. Krüll; M. G. Dehne; J. Gonter; S. Weiss; J. Engel; G. Hempelmann (pp. 39-53).
The objective of this study was to determine the effects of arginine, L-alanyl-L-glutamine (Ala-Gln) or taurine on polymorphonuclear leucocyte (PMN) free amino acid profiles, superoxide anion (O2 −) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase activity (MPO). Arginine led to significant increases in PMN arginine, ornithine, citrulline, aspartate, glutamate and alanine concentrations as well as increased H2O2-generation and MPO activity while O2 −-formation was decreased. Ala-Gln caused significant increases in PMN free glutamine, alanine, asparagine, aspartate, glutamate, ornithine, arginine, serine and glycine concentrations and increased PMN immune functions. Taurine significantly increased PMN free taurine profiles, reduced PMN neutral amino acid content and decreased H2O2- and O2 −-formation while MPO was increased. Altogether, the pharmacological regimens which enhance the supply of arginine, Ala-Gln or taurine in whole blood significantly affect PMN "susceptible free amino acid pool". This may be one of the determinants in PMN nutrition considerably influencing PMN immune functions.
Keywords: Keywords: Amino acids; Arginine; L-Alanyl-L-glutamine; Taurine; Neutrophil; Immune function
The classification of various organisms according to the free amino acid composition change as the result of biological evolution by K. Sorimachi (pp. 55-69).
The free amino acid compositions in archaeobacteria, eubacteria, protozoa, blue-green alga, green alga, slime mold, plants and mammalian cells were analyzed, to investigate whether changes in their free amino acid compositions reflect biological evolution. Cell homogenates were treated with 80–90% ethanol to separate cellular proteins and free amino acids contained in the cells. Different patterns of the free amino acid compositions were observed in the various organisms. Characteristic differences were observed between plant and mammalian cells, and between archaeobacteria and eubacteria. The patterns of the free amino acid composition in blue-green alga, green alga, protozoa and slime mold differed from each other and from those of eubacteria and archaeobacteria. Rat hepatoma cells (R-Y121B) were cultured in Eagle's minimum essential medium (MEM) containing 5% serum or in a modified MEM lacking arginine, tyrosine and glutamine. No significant difference in the free amino acid composition was observed between the two cell groups cultured under two different conditions. It is suggested that the free amino acid composition reflects apparent biological changes as the result of evolution.
Keywords: Keywords: Amino acids; Free amino acid composition; Nutrition; Archaea; Eubacteria; Eukaryotes
Synthesis, electrochemical and spectral properties of some ω-N-quinonyl amino acids by S. Bittner; S. Gorohovsky; O. Paz-Tal (Levi); J. Y. Becker (pp. 71-93).
Four series of ω-N-quinonyl amino acids were synthesized by Michael-like additions. The quinones include 2-phenylthio-1,4-benzoquinone, 1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone and 2,3-dichloro-1,4-naphthoquinone. These modified amino acids can be used for post chain assembly modifications of biologically active peptides, which target the quinonic drug to a cancer damaged area. The electron-transfer capabilities of the modified amino acids were probed by cyclic voltammetry measurements. The results described in this paper show that the novel N-quinonyl amino acids are effective in producing semiquinone radicals similarly to the unconjugated quinones themselves. A direct relation was found between the first reduction potentials of the quinones and their reactivity towards the ω-amino acids. The successful generation of stable semiquinone radicals by the novel quinone derivatives is a prerequisite for the manifestation of site-directed antitumor activity of corresponding quinone-peptide conjugates.
Keywords: Keywords: Amino acids; Quinones; Cyclic voltammetry; Redox potentials
Effect of alanyl-glutamine on leucine and protein metabolism in irradiated rats by M. Holeček; F. Skopec; L. Šprongl; J. Mráz; H. Skalská; M. Pecka (pp. 95-108).
The mechanism by which glutamine produces a favorable effect in the treatment of sepsis, injury, burns and abdominal irradiation is not completely understood. The main aim of this study was to evaluate the effect of alanyl-glutamine (AlaGln) administration on the metabolism of proteins in irradiated rats. The rats were exposed to whole-body irradiation (8 Gy) and then fed intragastrically with a mixture of glucose and amino acids either with AlaGln or without AlaGln. At 48 hours after irradiation, parameters of whole-body protein metabolism and DNA synthesis in intestinal mucosa were investigated using a primed, continuous infusion of [1-14C]leucine and [3H]thymidine. In addition, we evaluated the effect of irradiation and AlaGln on gut morphology, blood count and amino acid concentrations in blood plasma and skeletal muscle. Control rats were not irradiated but were given identical treatment. An increase in whole-body leucine oxidation, and insignificant changes in whole-body proteolysis and in protein synthesis were observed after irradiation. In irradiated rats we observed a decrease in muscle glutamine concentration, a decrease in protein synthesis in jejunum, colon and heart, and an increase in synthesis of proteins of blood plasma and spleen. Morphological examination and measurement of DNA synthesis failed to demonstrate any favorable effect of AlaGln supplementation on irradiated gut. However, administration of AlaGln resulted in a decrease in whole-body proteolysis and leucine oxidation which caused an increase in the fraction of leucine incorporated into the pool of body proteins. We conclude that the data obtained demonstrate that irradiation induces metabolic derangement associated with increased oxidation of essential branched-chain amino acids (valine, leucine and isoleucine) and that these disturbances can be ameliorated by administration of AlaGln.
Keywords: Keywords: Amino acids; Glutamine; Alanine; Ionising radiation; Leucine; Metabolism; Nutrition; Protein synthesis