Oxidation of meso-diaminosuccinic acid, a possible natural substrate for D-aspartate oxidase

Elution behavior of diaminopimelic acid and related diamino acids using the advanced Marfey's method

The advanced Marfey's method consists of a chromatography technique for the separation of amino acids into each enantiomer by derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-leucinamide (L-FDLA), and a detection method using liquid chromatography/mass spectrometry (LC/MS) which can determine the non-empirically the absolute configuration of various amino acids including the non-protein ones. However, this method has not been applied to the determination of the absolute configuration of an amino acid with a "meso" configuration such as diaminopimelic acid (A2pm). In the present study, this method was successfully applied to determine the absolute configurations of diaminosuccinic acid (DAS), A2pm, cystine (Cys), selenocystine (SeCys) and homocystine (HomoCys) using a racemization procedure and the DL-FDLA method, and the resulting elution behavior was summarized as follows: (1) the LL- and meso-isomers were eluted prior to the DD-isomer except for one case; (2) the LL- and meso-isomers are closely eluted and the elution was occasionally reversed; (3) the retention time for both the L- and D-derivatives of the meso-isomer was not changed; (4) the complementary use of the two solvent systems using CH3CN and MeOH was effective to obtain a chromatogram with a high resolution; (5) the abnormality, such as the elution order and peak shape, was observed in the elution behavior of DAS.

Purification of beef kidney D-aspartate oxidase overexpressed in Escherichia coli and characterization of its redox potentials and oxidative activity towards agonists and antagonists of excitatory amino acid receptors

The flavoenzyme d-aspartate oxidase from beef kidney (DASPO, EC 1.4. 3.1) has been overexpressed in Escherichia coli. A purification procedure, faster than the one used for the enzyme from the natural source (bDASPO), has been set up yielding about 2 mg of pure recombinant protein (rDASPO) per each gram of wet E. coli paste. rDASPO has been shown to possess the same general biochemical properties of bDASPO, except that the former contains only FAD, while the latter is a mixture of two forms, one active containing FAD and one inactive containing 6-OH-FAD (9-20% depending on the preparation). This results in a slightly higher specific activity (about 15%) for rDASPO compared to bDASPO and in facilitated procedures for apoprotein preparation and reconstitution. Redox potentials of -97 mV and -157 mV were determined for free and l-(+)-tartrate complexed DASPO, respectively, in 0.1 M KPi, pH 7.0, 25 degrees C. The large positive shift in the redox potential of the coenzyme compared to free FAD (-207 mV) is in agreement with similar results obtained with other flavooxidases. rDASPO has been used to assess a possible oxidative activity of the enzyme towards a number of compounds used as agonists or antagonists of neurotransmitters, including d-aspartatic acid, d-glutamic acid, N-methyl-d-aspartic acid, d,l-cysteic acid, d-homocysteic acid, d, l-2-amino-3-phosphonopropanoic acid, d-alpha-aminoadipic acid, d-aspartic acid-beta-hydroxamate, glycyl-d-aspartic acid and cis-2, 3-piperidine dicarboxylic acid. Kinetic parameters for each substrate in 50 mM KPi, pH 7.4, 25 degrees C are reported.

Free D-aspartate and D-serine in the mammalian brain and periphery

It has long been assumed that L-forms of amino acids exclusively constitute free amino acid pools in mammals. However, a variety of studies in the last decade has demonstrated that free D-aspartate and D-serine occur in mammals and may have important physiological function in mammals. Free D-serine is confined predominantly to the forebrain structure, and the distribution and development of D-serine correspond well with those of the N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptor. As D-serine acts as a potent and selective agonist for the strychnine-insensitive glycine site of the NMDA receptor, it is proposed that D-serine is a potential candidate for an NMDA receptor-related glycine site agonist in mammalian brain. In contrast, widespread and transient emergence of a high concentration of free D-aspartate is observed in the brain and periphery. Since the periods of maximal emergence of D-aspartate in the brain and periphery occur during critical periods of morphological and functional maturation of the organs, D-aspartate could participate in the regulation of these regulation of these developmental processes of the organs. This review deals with the recent advances in the studies of presence of free D-aspartate and D-serine and their metabolic systems in mammals. Since D-aspartate and D-serine have been shown to potentiate NMDA receptor-mediated transmission through the glutamate binding site and the strychnine-insensitive glycine binding site, respectively, and have been utilized extensively as potent and selective tools to study the excitatory amino acid system in the brain, we shall discuss also the NMDA receptor and uptake system of D-amino acids.

Distribution of D-aspartate oxidase and free D-glutamate and D-aspartate in chicken and pigeon tissues

The presence of D-aspartate oxidase activity and D-glutamate was demonstrated for the first time in several tissues of chicken and pigeon. 2. The identification of the enzyme was based on substrate and inhibitors specificity of the activity as well as other requirements for the activity, and the amino acid was identified with HPLC analysis. 3. In each animal, the highest activity was found in the kidney. In chicken, the hepatic, renal and pancreatic activities were significantly higher in male than female. In pigeon, however, any significant gender difference was not observed. 4. A substantial amount of D-glutamate, as well as D-aspartate, was detected in each tissue, irrespective of species. 5. The contents of the free D-enantiomers were significantly different between two genders in the chicken kidney, heart and pancreas and pigeon liver and kidney. However, any common relationship was not observed between the contents and the D-aspartate oxidase activity.

D-aspartate oxidase in rat, bovine and sheep kidney cortex is localized in peroxisomes

D-Aspartate oxidase (EC 1.4.3.1) was assayed in subcellular fractions and in highly purified peroxisomes from rat, bovine and sheep kidney cortex as well as from rat liver. During all steps of subcellular-fractionation procedures, D-aspartate oxidase co-fractionated with peroxisomal marker enzymes. In highly purified preparations of peroxisomes, the enrichment of D-aspartate oxidase activity over the homogenate is about 32-fold, being comparable with that of the peroxisomal marker enzymes catalase and D-amino acid oxidase. Disruption of the peroxisomes by freezing and thawing released more than 90% of the enzyme activity, which is typical for soluble peroxisomal-matrix proteins. Our findings provide strong evidence that in these tissues D-aspartate oxidase is a peroxisomal-matrix protein and should be added as an additional flavoprotein oxidase to the known set of peroxisomal oxidases.