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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.21, #4)

Protein expression in Down syndrome brain by E. Engidawork; G. Lubec (pp. 331-361).

Down syndrome (DS) is the most common chromosomal abnormality associated with early mental retardation and neurological abnormalities followed by precocious age dependent Alzheimer-type neurodegeneration later in life. Knowledge of the pathological mechanisms involved in DS is far from complete, but overexpression of genes residing in chromosome 21 was considered to be the central point for the DS phenotype. In this regard, ßamyloid precursor protein (APP), CuZn superoxide dismutase (SOD1) and S100β have been implicated in causing apoptosis, a mechanism thought to be responsible for neuronal loss in DS, in one way or another. The gene dosage hypothesis has been challenged, however, and dysregulation of expression of genes located on other chromosomes has been described, which may well be secondary to chromosomal imbalance or a direct consequence of the disease process. The present review focuses on the protein expression profile in DS and we postulate that abnormalities in the coordinated expression, as well as interaction of proteins may be responsible for the neuropathology of DS. A series of candidate proteins are discussed that may be directly causing or reflecting the DS phenotype, in particular the brain abnormalities in DS.

Keywords: Keywords: Down syndrome; Protein expression; Chromosome 21; Fetal brain; Neurodevelopment; Apoptosis; Oxidative stress

Proteomics: Current technologies and applications in neurological disorders and toxicology by M. Fountoulakis (pp. 363-381).

Proteomics is the science that studies the proteins in general and in particular their changes, resulting from various disorders or the effect of external factors, such as toxic agents. It has as goal the detection of novel drug targets, diagnostic markers and the investigation of biological events. Proteomics has emerged the last few years and its major difference from the previously existing protein analytical techniques is that it does not analyze the proteins one by one, but in a possibly automated, large-scale mode. In this article, the state of the art of proteomics in our laboratory is presented, as well as selected applications of proteomics in the study of disorders of the central nervous system and of toxic events.

Keywords: Keywords: Amino acids; 2-D electrophoresis; Neurological disorders; Matrix-assisted laser desortpion ionization mass spectrometry; Proteomics; Toxicology

Catabolism of methionine and threonine in vitro by mixed ruminal bacteria and protozoa by M. M. Or-Rashid; R. Onodera; S. Wadud; S. Oshiro; T. Okada (pp. 383-391).

In vitro studies were conducted to examine the metabolism of methionine (Met) and threonine (Thr) using mixed ruminal bacteria (B), mixed ruminal protozoa (P), and a combination of these two (BP). Rumen microorganisms were collected from fistulated goats fed with lucerne cubes (Medicago sativa) and a concentrate mixture twice a day. Microbial suspensions were anaerobically incubated with or without 1 mM each of the substrates at 39°C for 12 h. Met, Thr and their related amino compounds in both the supernatants and microbial hydrolyzates of the incubation were analyzed by HPLC. Met was degraded by 58.7, 22.1, and 67.3% as a whole in B, P, and BP suspensions, respectively, during 12 h incubation. In the case of Thr, these values were 67.3, 33.4, and 76.2% in B, P, and BP, respectively. Met was catabolized by all of the three microbial suspensions to methionine sulfoxide and 2-aminobutyric acid. Catabolism of Thr by B and BP resulted in the production of glycine and 2-aminobutyric acid, while P produced only 2-aminobutyric acid. From these results, the existence of diverse catabolic routes of Met and Thr in rumen microorganisms was indicated.

Keywords: Keywords: Amino acids; Rumen bacteria; Rumen protozoa; Meth-ionine; Threonine; 2-Aminobutyric acid

Conservation of the basic pattern of cellular amino acid composition of archaeobacteria during biological evolution and the putative amino acid composition of primitive life forms by K. Sorimachi; T. Itoh; Y. Kawarabayasi; T. Okayasu; K. Akimoto; A. Niwa (pp. 393-399).

Previous studies showed that the cellular amino acid composition obtained by amino acid analysis of whole cells, differs such as eubacteria, protozoa, fungi and mammalian cells. These results suggest that the difference in the cellular amino acid composition reflects biological changes as the result of evolution. However, the basic pattern of cellular amino acid composition was relatively constant in all organisms examined. In the present study, we examined archaeobacteria, because they are considered important in understanding the relationship between biological evolution and cellular amino acid composition. The cellular amino acid compositions of Archaeoglobus fulgidus, Pyrococcus horikoshii, Methanobacterium thermoautotrophicum and Methanococcus jannaschii differed slightly from each other, but were similar to those determined from codon usage data, based on the complete genomes. Thus, the cellular amino acid composition reflects biological evolution. We suggest that primitive forms of life appearing on earth at the end of prebiotic evolution had a similar-cellular amino acid composition.

Keywords: Keywords: Amino acids; Cellular amino acid composition; Evolution; Archaea; Codon frequency; Primitive life forms

The effect of high protein diet on urea and guanidino compound levels in renal insufficient mice by M. Al Banchaabouchi; B. Marescau; R. D'Hooge; P. P. De Deyn (pp. 401-415).

Nephrectomy in mice provokes a decrease in creatinine clearance (CTN_Cl) and an increase in urea and specific guanidino compound (GC) concentrations in blood and other tissues. Our purpose was to investigate the influence of high protein diet (HPD) on CTN_Cl, urea and GC levels in NX mice. Mice were nephrectomized or sham-operated and subdivided in groups to study five diet conditions. At the end of each experiment, 10 days and 30 days postsurgery, urine and blood were collected for determination of urea and GCs, including creatinine. HPD resulted in significantly higher CTN_Cl values in sham-operated mice than those observed in mice under normal protein diet, 10 days as well as 30 days postnephrectomy. HPD induced significant increases in plasma urea, guanidinosuccinic acid, argininic acid and α-keto-δ-guanidinovaleric acid concentration 10 days postsurgery but not 30 days postsurgery. HPD coincided with significantly higher excretion of urea, guanidinosuccinic acid, α-keto-δ-guanidinovaleric acid, creatine, argininic acid and γ-guanidinobutyric acid in sham-operated and nephrectomized mice 10 days postsurgery. Our results show that HPD induces supplementary (to nephrectomy) increases of urea and GCs in the early postsurgery period but not in the later phase.

Keywords: Keywords: Amino acids; High protein diet; Guanidino compound levels; Nephrectomy; Mice; Renal insufficiency

Kinetics of taurine depletion and repletion in plasma, serum, whole blood and skeletal muscle in cats by L. Pacioretty; M. A. Hickman; J. G. Morris; Q. R. Rogers (pp. 417-427).

The relationship between taurine concentrations of plasma, whole blood, serum and skeletal muscle during taurine depletion and repletion was investigated in cats, to identify the most useful indicators of taurine status. Sixteen cats were fed a purified diet containing either 0 or 0.15 g/kg taurine for 5 months. Treatments were then reversed and the taurine concentration was measured during repletion and depletion phases. Plasma taurine exhibited the fastest rate (slow component) of depletion (t_1/2 = 4.8 wk), followed by serum (5.3 wk), whole blood (6.2 wk), and skeletal muscle (11.2 wk). Whole blood taurine was the first to replete at a rate of 0.74 wk to ½ maximal repletion, followed by serum (2.1 wk), skeletal muscle (3.5 wk), and plasma (3.5 wk). Whole blood more closely reflected skeletal muscle taurine concentrations than plasma during depletion, while plasma taurine concentrations appear to be the most valuable predictor of skeletal muscle taurine concentrations during repletion. This study suggests that the best clinical method to evaluate the taurine status of the cat is the determination and interpretation of both plasma and whole blood taurine concentrations.

Keywords: Keywords: Amino acids; Taurine; Taurine depletion; Taurine repletion; Cats; Feline

Saccharide induced racemization of amino acids in the course of the Maillard reaction by H. Brückner; J. Justus; J. Kirschbaum (pp. 429-433).

The formation of D-amino acids on heating aqueous solutions of protein L-amino acids at pH 2.5 and pH 7.0 together with glucose, fructose or saccharose was investigated by enantioselective gas chromatography. The saccharide induced partial racemization (epimerisation) of L-amino acids is attributed to the Maillard reaction.

Keywords: Keywords: D-amino acids; Maillard reaction; Nonenzymic browning; Racemization mechanism; Saccharides (glucose; fructose; saccharose); Gas chromatography; Chirasil-L-Val

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.21, #4)

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.21, #4)