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D Cavallini

Publications and source records attributed to D Cavallini.

At least 37 records · Page 2Linked to original sources
PubMed1994

Aminoethylcysteine ketimine decarboxylated dimer inhibits mitochondrial respiration by impairing electron transport at complex I level.

The product of the spontaneous dimerization and decarboxylation of aminoethylcysteine ketimine (simply named the dimer in this note) has been investigated for a possible biochemical activity. It has been found that the dimer inhibits the ADP-dependent oxidation of NAD(+)-linked substrates in rat liver mitochondria and electron transport from NADH to O2 in bovine heart submitochondrial particles (SMP). Oxidation of succinate by SMP is not impaired by concentrations of the dimer inhibiting almost totally NADH oxidation. Furthermore, the dimer did not affect the rotenone-insensitive electron transfer from NADH to menadione. These results give a preliminary indication suggesting that the dimer inhibits electron flow from NADH dehydrogenase to ubiquinone at or near the rotenone binding site(s). The dimer inhibition falls in the same range exhibited by some neurotoxins which are known to interact with the rotenone binding site.

Animals↗
PubMed1994

The in vitro and in vivo effect of recombinant interferon alpha-2a on circulating haemopoietic progenitors in polycythaemia vera.

In four patients with polycythaemia vera (PV) who received interferon alpha (IFN-alpha) (3 MU subcutaneously three times a week) for 5 months, peripheral blood levels of granulocyte-macrophage colony-forming units and erythroid burst-forming units were assessed monthly. Circulating progenitors significantly decreased throughout the treatment period. Moreover, we observed an inhibitory activity of IFN-alpha on haemopoietic progenitor cells (HPC) from patients with PV in vitro. The data presented confirm previous research which has shown an inhibitory effect of IFN-alpha on HPC from patients with myeloproliferative disorders. Significant improvement in the patients' clinical and haematological conditions should encourage larger studies on IFN-alpha administration in PV patients.

Aged↗
PubMed1993

Characterization of [35S]lanthionine ketimine specific binding to bovine brain membranes.

[35S]Lanthionine ketimine binds specifically and with high affinity to bovine brain membranes. This binding has been studied in detail. It is reversible, not occurring at an uptake site or at a metabolizing enzyme and depending only weakly from ionic strength; it is affected by thiol reagents. [35S]Lanthionine ketimine specific binding is displaced only by other ketimines and by catecholamines, but not by more selective adrenergic ligands; binding parameters are reported. [3H]Adrenaline but not [3H]dihydroalprenolol is partially displaced by lanthionine ketimine. With bovine brain preparations a significant stimulation of basal adenylate cyclase activity by lanthionine ketimine is observed.

Adenylyl Cyclases↗
PubMed1993

The oxidative deamination of L-aminoethylcysteine sulfoxide and sulfone by snake venom L-amino acid oxidase.

The oxidation of L-aminoethylcysteine (AEC) by L-amino acid oxidase has been compared with that of the respective sulfoxide (AEC-SO) and sulfone (AEC-SO2). Spectral and HPLC analyses of the incubates reveal the formation of the respective cyclic ketimines. While the ketimine coming from AEC is subjected to autooxidation yielding the sulfoxide and other products, the ketimines produced from AEC-SO and AEC-SO2 are more stable and account for almost the total conversion of the substrate in the product. Spectrophotometric and HPLC properties of the ketimine produced from AEC-SO are identical to those reported earlier for the main product of the autooxidation of AEC ketimine, thus confirming its identification. These results could explain the presence of chondrine in biological materials as a product of reduction of AEC-SO ketimine.

Amino Acid Oxidoreductases↗
PubMed1993

The inhibition of bovine serum amine oxidase by cysteamine.

Bovine serum amine oxidase (BSAO) is inhibited by cysteamine, while cystamine is a good substrate. The activity of BSAO is not restored following removal of excess cysteamine by N-ethylmaleimide, by iodoacetate or by filtration through a G-25 Sephadex column.

Animals↗
PubMed1992

The reducing activity of S-aminoethylcysteine ketimine and similar sulfur-containing ketimines.

S-aminoethylcysteine ketimine and other sulfur-containing similar ketimines reduce molecular oxygen and phospho-18-tungstate (Folin Marenzi reagent), although the sulfur atom is formally present in the non reducing thioether form. We have now found that 2,6-diclorophenolindophenol, some ferrihemoproteins and other reagents are also reduced by this group of ketimines. Ferricytochrome c is reduced faster than methemoglobin, metmyoglobin and free hematin, whereas horse radish peroxidase compound I is reduced at once. These results indicate a wider reducing activity of this type of ketimine. The oxidation of ketimines by ferric cytochrome c appears a relevant finding pointing to a new possible way of enzymatic modification of sulfur-ketimines in tissues.

2,6-Dichloroindophenol↗
PubMed1992

Enzymatic synthesis of S-aminoethyl-L-cysteine from pantetheine.

The recently characterized compound S-aminoethylcysteine ketimine can be synthesized from purified S-aminoethylcysteine by enzymatic systems (transaminases or L-amino acid oxidase) present in mammalian tissues. S-Aminoethylcysteine, which could be considered as the natural precursor of the ketimine, is produced from L-serine and cysteamine by the action of the enzyme cystathionine-beta-synthase. We demonstrate in this paper that pantetheine, a normal cellular component, is an efficient cysteamine donor for the synthesis of S-aminoethylcysteine and of S-aminoethylcysteine ketimine in the place of free cysteamine, and we describe the enzymatic system, composed of partially purified enzymes, for the in vitro synthesis of S-aminoethylcysteine ketimine from pantetheine. This seems to indicate a new biological role for pantetheine.

Amidohydrolases↗
PubMed1991

Sulfur-containing cyclic ketimines and imino acids. A novel family of endogenous products in the search for a role.

Aminoethylcysteine, lanthionine, cystathionine and cystine are mono-deaminated either by L-amino-acid oxidase or by a transaminase exhibiting the properties described for glutamine transaminase. The deaminated products cyclize producing the respective ketimines. Authentic samples of each ketimine were prepared by reacting the appropriate aminothiol compound with bromopyruvate, except cystine ketimine which required the interaction of thiopyruvate with cystine sulfoxide. Reduction of the first three mentioned ketimines with NaBH4 yields the respective derivatives with the saturated rings of thiomorpholine and hexahydrothiazepine. The same reduction is carried out enzymically by a reductase extracted from mammalian tissues. Properties of the members of this family of compounds are described. Gas chromatography followed by mass spectrometry permits the identification of most of these products. HPLC is very useful for the determination of the ketimines by taking advantage of specific absorbance at 380 nm obtained by prior derivatization with phenylisothiocyanate. Adaptation of these and other analytical procedures to biological samples disclosed the presence of most of these compounds in bovine brain and in human urine. By using [35S]lanthionine ketimine as a representative member of the ketimine group, the specific, high-affinity, saturable and reversible binding to bovine brain membranes has been demonstrated. The binding is removed by aminoethylcysteine ketimine and by cystathionine ketimine indicating the occurrence in bovine brain of a common binding site for ketimines. The reduced ketimines are totally ineffective in competing with [35S]lanthionine ketimine. Alltogether these findings are highly indicative for the existence in mammals of a novel class of endogenous sulfur-containing cyclic products provided with a possible neurochemical function to be investigated further.

Amino Acids, Sulfur↗
PubMed1991

Dimerization and other changes of aminoethylcysteine ketimine.

High performance liquid chromatography and gas liquid chromatography have been used for the study of the stability of aminoethylcysteine-ketimine (AECK) in different experimental conditions. Concentration and acidic pH lead to the formation of the dimer of AECK which is very sensitive to temperature and is slowly converted to the corresponding decarboxylated dimer even at room temperature. In the presence of air at neutral and alkaline pH AECK is converted to an unknown compound having spectral characteristics similar to AECK and to other compounds not detectable by HPLC. Under nitrogen at neutral pH AECK is more stable and only undergoes the dimerization reaction to some extent.

Amino Acids, Sulfur↗
PubMed1990

[35S]Lanthionine ketimine binding to bovine brain membranes.

2H-1,4-Thiazine-5,6-dihydro-3,5-dicarboxylic acid (trivial name: lanthionine ketimine) is a cyclic sulfur-containing imino acid detected in bovine brain extracts. This compound has been synthesized in a heavily labeled form starting from L-[35S]cysteine and purified by high performance liquid chromatography. We demonstrate the existence of a saturable and reversible binding of [35S]lanthionine ketimine to bovine brain membranes. A single population of binding sites with a concentration of 260 +/- 12 fmol/mg protein and a dissociation constant of 58 +/- 14 nM is present. Specific binding is competitively inhibited by other structurally similar imino acids, namely S-aminoethyl-L-cysteine ketimine and cystathionine ketimine. These results suggest a possible functional role for these ketimines in nervous system.

Amino Acids, Sulfur↗
PubMed1990

Detection of 2H-1,4-thiazine-5,6-dihydro-3-carboxylic acid (aminoethylcysteine ketimine) in the bovine brain.

2H-1,4-Thiazine-5,6-dihydro-3-carboxylic acid (trivial name: aminoethylcysteine ketimine) is a cyclic sulfur-containing imino acid detected in bovine brain extracts by means of three different procedures. Gas liquid chromatography of protein-free extracts of five bovine brains revealed the presence of this compound at concentrations ranging from 2 to 3 nmol/g wet weight of tissue. The enzymatic method based on the inhibition of D-amino acid oxidase activity by aminoethylcysteine ketimine together with an high-performance liquid chromatography procedure confirm the identification and quantitations obtained with gas liquid chromatography. The discovery of this compound structurally similar to pipecolic acid opens the question of its physiological role in the central nervous system.

Amino Acids, Sulfur↗
PubMed1990

Detection of cystathionine ketimine in bovine cerebellum.

A new sulfur-containing cyclic imino acid, cystathionine ketimine, has been detected in bovine cerebellum by gas chromatography, gas chromatography-mass spectrometry, and high pressure liquid chromatography procedures. Gas chromatography and gas-mass analyses are based on derivatization of endogenous cystathionine ketimine with diazomethane after a simple enrichment procedure. The high pressure liquid chromatography procedure takes advantage of the selective absorbance at 380 nm of the phenyl isothiocyanate-ketimine interaction product. The concentration of this new sulfur imino acid found in a pool of four bovine cerebella is approximately 0.5 nmol/g.

Animals↗
PubMed1989

Identification of 1,4-thiomorpholine-3-carboxylic acid (TMA) in normal human urine.

The sulfur-containing cyclic imino acid 1,4-thiomorpholine-3-carboxylic acid (TMA) has been identified in normal human urine. After the enrichment procedure with ion-exchange chromatography, the urine extracts were reacted with diazomethane. Gas-liquid chromatography revealed the presence of two peaks with the same retention times exhibited by authentic TMA after the same derivatization. The two compounds have been identified by mass-spectrometry as the monomethylated and dimethylated derivatives of TMA. This result represents the first indication of the occurrence of TMA in a mammalian sample.

Gas Chromatography-Mass Spectrometry↗
PubMed1989

Detection of 2H-1,4-thiazine-5,6-dihydro-3,5-dicarboxylic acid (lanthionine ketimine) in the bovine brain by a fluorometric assay.

A new sulfur imino acid, 2H-1,4-thiazine-5,6-dihydro-3,5-dicarboxylic acid (lanthionine ketimine), has been detected in the bovine brain by means of fluorometric and HPLC procedures. The fluorometric assay is based on the fluorescent property of the copper-ketimine interaction product at pH 11.5. Other ketimines do not fluoresce in these conditions. The fluorophore exhibits an excitation maximum at 353 nm and an emission at 462 nm and is stable for at least 24 h. In the test conditions the fluorescence is proportional to the ketimine concentration from 1 to 200 microM. Detection of endogenous lanthionine ketimine has been performed after a simple enrichment procedure (brain deproteinization and extraction with diethyl ether) which minimizes degradative by-reactions of the unstable ketimine. The concentration of this new sulfur imino acid in the brain ranges from 0.5 to 1 nmol/g in three different samples. Identification and quantitations were confirmed by an HPLC procedure which takes advantage of the selective absorption at 380 nm of the phenylisothiocyanate-ketimine adduct. The identification of lanthionine ketimine in nervous tissues may have important metabolic and physiological implications.

Amino Acids, Sulfur↗
PubMed1988

Bovine brain ketimine reductase.

We report the purification from bovine brain of an NAD(P)H-dependent reductase which actively reduces a new class of cyclic unsaturated compounds, named ketimines. Ketimines arise from the transamination of some sulphur-containing amino acids, such as L-cystathionine, S-aminoethyl-L-cysteine and L-lanthionine. The enzyme also reduces delta 1-piperidine 2-carboxylate, the carbon analog of aminoethylcysteine ketimine. Some kinetic and molecular properties of this enzyme have been determined. Subcellular localization and regional brain distribution have also been studied. The ketimine reductase activity was found to be associated with the soluble fraction, and was located prevalently in the cerebellum and cerebral cortices. Cyclothionine and 1,4-thiomorpholine-3,5-dicarboxylic acid, the enzymatic reduction products of cystathionine ketimine and lanthionine ketimine, respectively, have been detected in bovine brain, thus suggesting a role of this enzyme in their biosynthesis.

Animals↗