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PubMed1965

INCORPORATION OF C14 FROM CARBON DIOXIDE INTO SUGAR PHOSPHATES, CARBOXYLIC ACIDS, AND AMINO ACIDS BY CLOSTRIDIUM THERMOACETICUM.

Ljungdahl, Lars (Western Reserve University, Cleveland, Ohio), and Harland G. Wood. Incorporation of C(14) from carbon dioxide into sugar phosphates, carboxylic acids, and amino acids by Clostridium thermoaceticum. J. Bacteriol. 89:1055-1064. 1965.-The mechanism of synthesis of acetate from carbon dioxide by Clostridium thermoaceticum was investigated by incubating cells with glucose or xylose in the presence of C(14)O(2). Sugar phosphates, amino acids, and carboxylic acids were isolated and the specific radioactivities were determined; the distributions of C(14) were also determined in some of the compounds. Only fructose-1,6-diphosphate, formate, and lactate had higher specific activities than the acetate. The specific activities and distribution of C(14) in the fructose-6-phosphate and ribose-5-phosphate were such that we conclude that the synthesis of acetate does not occur via a pathway involving the sugar phosphates as direct intermediates. Likewise, it is shown that pathways including lactate, aspartate, serine, glycine, malate, and succinate are not of importance in the synthesis of acetate from CO(2). The methyl group of free methionine was unlabeled and is not a precursor of the methyl group of acetate.

Acetates↗
PubMed1994

Investigation of "signal" constituents for the evaluation of animal crude drugs. I. Free amino acids and total amino acids.

The contents of free amino acids (FAA) and total amino acids (TAA; including peptide and protein forms) in 10 animal drugs were determined using precolumn-derivatization high performance liquid chromatography (HPLC). The results showed that the FAA and TAA content was characteristic for a particular animal crude drug. For example, Bezoar Bovis contained much more taurine relative to the FAA and TAA content compared with other crude drugs, and kokurozin contained much more TAA and much less secondary amino acids relative to TAA compared with koukuzin. FAA and TAA were proved to be "signal" constituents for the evaluation of animal crude drugs.

Amino Acids↗
PubMed1989

Metabolic derangement of glucose, bile acid and amino acids after portasystemic shunts in cirrhotic rats.

Carbon tetrachloride was used to induce cirrhosis in 81 Wistar rats. The animals were divided into three groups to receive end-to-side mesocaval shunt (MCS), end-to-side portacaval shunt (PCS) and Sham operation as control, respectively. Dynamic values of blood glucose and hormones for regulating glucose metabolism, SGPT, serum glycine conjugated cholic acid (CCA) and free serum amino acids were determined and compared with those obtained from 10 normal rats. The determinations suggested that the insulin level depended on the severity of hepatocellular damage with hyperglucagonemia after portasystemic shunt, and CCA was markedly elevated in MCS rats after interruption of the enterohepatic circulation. Changes of CCA were also influenced by hyperglucagonemia and poor liver function in PCS rats. Increase in the aromatic amino acids (AAA) level was related to the impaired hepatic function and hyperglucagonemia. However, decrease in the branched-chain amino acids (BCAA) level was not likely in response to the serum insulin level. Therefore, it is concluded that imbalance of serum amino acids has partial relationship with the derangement of glucose metabolic hormones.

Amino Acids↗
PubMed1976

Acid-labile amino acid precursors in the Murchison meteorite. 1: Chromatographic fractionation.

The amino acid content of a hot water extract of the Murchison meteorite can be increased by over 100 per cent by subjecting the extract to acid hydrolysis. The acid-labile compounds in the extract that account for this increase were fractionated by column chromatography on a cation exchange resin. Seventy mole per cent behaved as neutral or acidic compounds and were eluted from the column with an initial water wash. The remaining 30 mole per cent (basic precursors) were retained on the column and were eluted with the free amino acids by aqueous NH4OH. The acid-labile amino acid precursors in the water eluate could be retained and further fractionated on an anion exchange column, indicating that they are acidic compounds.

Acids↗
PubMed1996

Inhibition of D-amino acid oxidase by alpha-keto acids analogs of amino acids.

The inhibition of D-amino acid oxidase by certain alpha-keto acids products of the reaction with D-amino acids, in particular alpha-keto acids that are analogs of the amino acids alanine, valine, leucine, phenylanaline, phenylglycine, tyrosine and tryptophan, is reported. All the alpha-keto acids assayed behaved as substrate competitive inhibitors of the enzyme. The relationship between the degree of inhibition and the structure of the inhibitor is discussed.

Amino Acids↗
PubMed1997

Effects of source of starch on net portal flux of glucose, lactate, volatile fatty acids and amino acids in the pig.

The ileal digestibilities of maize starch and native pea starch do not differ. However maize starch is digested faster than pea starch and the ileal amino acid digestibility of a diet containing pea starch is lower. In the present study, the net portal fluxes of glucose, lactate, volatile fatty acids (VFA) and amino acids were measured for diets including 650 g maize starch or pea starch/kg. The diets were fed at a level 870 kJ digestible energy/kg0.75 twice daily (06.00 and 18.00 hours) to four female pigs in a crossover design. Portal vein blood flow did not differ between maize and pea starches (1620 and 1484 ml/min respectively; SED 100; P = 0.23). For maize starch portal glucose flux was significantly higher during the first 6 h after feeding, was not different 8 h after feeding and was significantly lower thereafter. Net portal glucose flux was higher for maize starch than for pea starch (1759 and 1265 mmol/12 h respectively; SED 182; P = 0.054). Net portal lactate flux was not significantly different between maize and pea starches (36.5 and 67.2 mmol/12 h respectively; SED 24.1; P = 0.27) and net portal VFA flux was lower for maize starch than for pea starch (169 and 218 mmol/12 h respectively; SED 18; P = 0.054). Net portal fluxes of valine, isoleucine, phenylalanine, tryptophan, arginine, serine, cystine, tyrosine, lysine, histidine and the sum of essential amino acids tended to be or were higher (P < 0.1 or P < 0.05) and net portal flux of aspartic acid tended to be lower for pea starch (P < 0.1). It can be concluded that, although ileal digestibility of both starches is equal, the rate of appearance of glucose in the portal vein was higher for maize starch, influencing the net portal flux of amino acids.

Amino Acids↗
PubMed1984

Enhanced intestinal absorption of amino acids and amino acid-like drug by possible formation of enamine in administered solution by the presence of ethylacetoacetate.

Ethylacetoacetate promoted the colonic and the jejunal absorption of amino acids such as L-phenylalanine and D-phenylalanine when administered in aqueous solution. Enhanced absorption of these isomers of amino acid might occur via a formation of enamine, which was observed in aqueous solution by monitoring ultraviolet absorbance at 288 nm. Since mixture of L- or D-phenylalanine and ethylacetoacetate in aqueous solution enhanced colonic absorption of cefmetazole while the solution did not affect so much on the jejunal absorption of cefmetazole compared to the colonic absorption of it, enhancing action of enamine probably produced in aqueous solution may be more effective at the colonic compartment.

Acetoacetates↗
PubMed1993

Racemization during aminolysis of activated esters of N-alkoxycarbonylamino acids by amino acid anions in partially aqueous solvents and a tactic to minimize it.

Racemization during the aminolysis of activated esters of N-alkoxycarbonylamino acids by amino acid anions in aqueous dimethylformamide was examined by determining the epimeric products by high-performance liquid chromatography. Partial racemization occurred for a variety of esters, particularly when sodium hydrogen carbonate was used to generate the anion of D-valine. The racemization results from prolonged contact of unconsumed ester with the alkaline medium. Variation of the stoichiometry of reagents for reactions with N-benzyloxycarbonylphenylalanine (Z-Phe) 4-nitrophenyl ester revealed that racemization could be minimized by using Na2CO3 as base and a 50% excess of amino acid anion. An efficient synthesis of optically pure Z-L-Phe-D-Val-OH was achieved with a reaction time of 15 min.

Amino Acids↗
PubMed1984

Comparison of the effect of semisynthetic human insulin and porcine insulin on glucose kinetics, plasma free fatty acid and amino acid levels in man.

The effect of semisynthetic human insulin on hepatic glucose output, peripheral glucose clearance, plasma levels of C-Peptide, free fatty acids and amino acids was compared with purified pork insulin using the glucose clamp technique. 8 normal overnight-fasted subjects received intravenous infusions of either human or porcine insulin at 20 mU/m2.min(-1) during 120 min achieving plasma insulin levels of approximately equal to 50 mU/l. Plasma glucose levels were maintained at euglycaemia by variable rates of glucose infusion. Hepatic glucose production measured by continuous infusion of 3-(3) H-glucose was similarly suppressed by both insulins to rates near zero. The metabolic clearance rate of glucose increased during infusion of human insulin by 120%, C-peptide levels decreased by 41% and plasma FFA concentrations fell by 74%. The respective changes during infusion of pork insulin were similar, 118%, 48% and 72%. Both insulins decreased the plasma levels of branched-chain amino acids, tyrosine, phenylalanine, methionine, serine and histidine similarly. Thus, the results demonstrate that semisynthetic human and porcine insulin are aequipotent with respect to suppression of hepatic glucose output, stimulation of glucose clearance, inhibition of insulin secretion, lipolysis and proteolysis.

Aged↗
PubMed1998

Increase in thermostability of N-carbamyl-D-amino acid amidohydrolase on amino acid substitutions.

To improve the production of D-amino acids using an immobilized N-carbamyl-D-amino acid amidohydrolase, the enzyme gene of Agrobacterium sp. KNK712 was mutagenized randomly to increase its thermostability. The gene was inserted into M13mp19, mutagenized with hydroxylamine, ligated into pUC19 after restriction endonuclease digestion, and then used to transform Escherichia coli. The resultant transformants were screened by a newly developed colorimetric enzyme assay method, and the candidate colonies corresponding to red spots were separated from the master plates. Using cell-free extracts of these clones, the properties of the enzymes produced were investigated, it being proved that these enzymes had almost the same activity and improved thermostability by about 5 degrees C compared with those of the native enzyme. As found on enzyme gene analysis of these mutants, the 57th amino acid, histidine, of the enzyme was changed to tyrosine, or the 203rd amino acid, proline, to leucine or serine.

Amidohydrolases↗
PubMed1982

The intracellular acid-extractable (acid-soluble) amino acid pool in mammalian cells. 1 Extractability.

The acid-extractable pool in mammalian cells is composed of amino acids bound to or complexed with other molecules, possible proteins. It does not appear to consist of free amino acid molecules restrained within the cell by a supposedly impermeable plasma membrane. Attempts to characterize the pool have involved permeabilizing cells to macromolecules by standard procedures, and extraction of amino acids by a variety of chemical and physical methods. The molecules seem to be held by covalent bonds of a partially ionic nature, or in the form of a complex which may involve more than one other moiety. Simple ionic and hydrogen bonding have been ruled out, and disulphide bonds are not involved. Pools can be as effectively extracted with the lower alcohols as with organic acids. Further characterization will require the exceedingly difficult task of releasing amino acids from cells without disrupting their links with other moieties. The findings are consistent with the behaviour of pools in relations to protein synthesis (Wheatley and Inglis, 1980), and may also explain differential discharge kinetics.

Amino Acids↗
PubMed1981

Disposition of the acid-extractable amino acid pool in mammalian cells.

Experimental evidence is presented which eliminates the acid-extractable (acid-soluble) pool of amino acids within cells from being the source of precursor molecules for protein synthesis. This is equally valid for those amino acids initially showing quasi-exponential incorporation into protein, viz, glycine and proline, contrary to the reports of others (e.g. Robinson, 1977). Reexamination of the design of some of the experiments showing the pool acting as the precursor supply has revealed technical defects which may have been responsible for this erroneous conclusion. The acid-extractable pool can be more clearly understood as the accumulation of complexed amino acids which have passed the selection mechanism of the intracellular cyclical perfusion system (Wheatley and Inglis, 1980), but are no longer directly available for protein synthesis.

Amino Acids↗
PubMed1986

Kinetic study of the reaction between trinitrobenzenesulfonic acid and amino acids with a trinitrobenzenesulfonate ion-selective electrode.

Potentiometric studies of the reaction between trinitrobenzenesulfonic acid (TNBS) and several amino acids with the TNBS electrode indicate that the reaction is first-order with respect to TNBS and amino acid concentration. The reaction is zero-order with respect to hydroxide concentration at pH greater than 10.5, indicating that the nonprotonated amino group is the reactive species. Rate constants were calculated for each amino acid and a simple mechanism of the reaction is proposed.

Alanine↗
PubMed2006

The significance of amino acids and amino acid-derived molecules in plant responses and adaptation to heavy metal stress.

Plants exposed to heavy metals accumulate an array of metabolites, some to high millimolar concentrations. This review deals with N-containing metabolites frequently preferentially synthesized under heavy metal stress such as Cd, Cu, Ni, and Zn. Special focus is given to proline, but certain other amino acids and oligopeptides, as well as betaine, polyamines, and nicotianamine are also addressed. Particularly for proline a large body of data suggests significant beneficial functions under metal stress. In general, the molecules have three major functions, namely metal binding, antioxidant defence, and signalling. Strong correlative and mechanistic experimental evidence, including work with transgenic plants and algae, has been provided that indicates the involvement of metal-induced proline in metal stress defence. Histidine, other amino acids and particularly phytochelatins and glutathione play a role in metal binding, while polyamines function as signalling molecules and antioxidants. Their accumulation needs to be considered as active response and not as consequence of metabolic dys-regulation.

Acclimatization↗
PubMed2005

Bile acid coenzyme A: amino acid N-acyltransferase in the amino acid conjugation of bile acids.

Bile acids are converted to their glycine and taurine N-acyl amidates by enzymes in the liver in a two-step process. This increases their aqueous solubility, particularly in the acidic environment of the upper part of the small intestine. Bile acid coenzyme A (CoA) thioesters synthesized by bile acid CoA ligase (see Shonsey et al., 2005) are substrates of bile acid CoA:amino acid N-acyltransferases (BAT) in the formation of bile acid N-acyl amidates. This chapter describes the methods used to purify BAT from human liver, to isolate and clone cDNAs encoding BAT from human, mouse, and rat liver cDNA libraries, the expression of BAT, the assays used to measure BAT activity, and the chemical syntheses of bile acid N-acylamidates. In addition, an enzyme that catalyzes further metabolism of glycine-conjugated bile acids is described.

Acyltransferases↗
PubMed2004

Influence of starter culture ratios and warm room treatment on free fatty acid and amino acid in Swiss cheese.

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.

Amino Acids↗
PubMed1999

Xenogeneic, extracorporeal liver perfusion in primates improves the ratio of branched-chain amino acids to aromatic amino acids (Fischer's ratio).

In fulminant hepatic failure (FHF), the development of hepatic encephalopathy is associated with grossly abnormal concentrations of plasma amino acids (PAA). Normalization of the ratio of branched-chain amino acids to aromatic amino acids (Fischer's ratio) correlates with clinical improvement. This study evaluated changes in PAA metabolism during 4 h of isolated, normothermic extracorporeal liver perfusion using a newly designed system containing human blood and a rhesus monkey liver. Bile and urea production were within the physiological range. Release of the transaminases AST, ALT and LDH were minimal. The ratio of branched (valine, leucine, isoleucine) to aromatic (tyrosine, phenylalanine) amino acids increased significantly. These results indicate that a xenogeneic extracorporeal liver perfusion system is capable of significantly increasing Fischer's ratio and may play a role in treating and bridging patients in FHF in the future.

Alanine Transaminase↗