Spyridon G.A. Alivisatos

Non-enzymic reactions of indoles with pyridine coenzymes and related structures☆

Abstract Certain compounds with “onium”-bearing structures, including diphosphopyridine nucleotide, interact non-enzymically with various indoles, including serotonin and tyrptophan. The products of these interactions are most probably of the charge-transfer complex type. The dependence of these associations on various other groupings present in the interacting species have been studied. Such groupings include the ethylamine residue present in serotonin, the 6-aminopurine moiety of diphosphopyridine nucleotide and the phosphate and pyrophosphate radicals present in the pyridine co-enzymes. An insight into the mechanism of these interactions on the molecular level might be gained by studies of the influence of the composition of the medium (methanol-water, etc.) on the optical properties of N-methylnicotinamide iodide-tryptamine mixtures.

Ontogeny of multiple forms of monoamine oxidase in mouse brain.

MAO activities in mouse brain responsible for deamination of serotonin (5-HT) and p-dimethylaminobenzylamine (DAB) were found to follow different postnatal developmental patterns. MAO activity which deaminated 5-HT reached adult levels 15 days after birth. At this age the capacity of brain to deaminate DAB was only 50% of adult levels and did not develop fully until after the 45th postnatal day. Inhibitor studies with Deprenil and clorgyline indicated that the deamination of the two substrates was due to different forms of MAO and that these forms were similar to type A and type B MAO described previously in rat brain.

NON-ENZYMATIC INTERACTIONS OF REDUCED COENZYME I WITH INORGANIC PHOSPHATE AND CERTAIN OTHER ANIONS.

WE previously reported1 changes of the absorption spectrum of nicotinamide adenine dinucleotide (coenzyme I, abbreviated NAD+) in solutions containing orthophosphate. In an extension of those investigations2, it has been observed that dihydronicotinamide-adenine dinucleotide (reduced coenzyme I, abbreviated NADH) also reacts with orthophosphate, but in an entirely different manner. Similar changes were observed with dihydronicotinamide adenine dinucleotide phosphate (reduced coenzyme II, abbreviated NADPH) and certain other NADH-analogues. This is a preliminary report of our findings3.

Inhibition of binding of aldehydes of biogenic amines in tissues

Abstract The binding of aldehydes derived from the biogenic amines (i.e. serotonin, dopamine, tryptamine, etc.) is dependent on the substituents attached to the carbonyl residue, as well as the aldehydic group per se . The hydroxyl group on the aromatic nucleus of “biogenic” aldehydes contributes significantly to the attachment of the moieties to brain tissue. Thus, 5-hydroxyindole and catechol were found to compete selectively with the “biogenic” aldehydes for tissue binding sites. The attachment of the “biogenic” aldehydes to tissue may also be prevented in vitro by various reducing or trapping agents, such as ascorbate, cysteine or glutathione. The possible physiologic significance of aldehyde binding to cellular components is discussed.

Biogenic aldehyde metabolism relation to pentose shunt activity in brain.

Abstract Biogenic amines, added to brain homogenates, were demonstrated to stimulate oxidative decarboxylation of glucose isotopically labeled at C-1. This effect was ascribed to the stimulation of the pentose phosphate shunt in brain and was found to depend on the monoamine oxidase (MAO)-catalyzed production of the aldehyde derivatives (biogenic aldehydes) of the biogenic amines. The stimulation produced by the amines and the aldehydes was shown to be inhibited by barbiturates, and the enzymes responsible for the stimulated metabolism of glucose were found to be present in the cytosol. Evidence is presented indicating that the stimulation produced by biogenic aldehydes depends on the oxidation of NADPH to NADP by aldehyde reductase present in brain cytosol. Acid derivatives of the biogenic amines [i.e. 5-hydroxyindoleacetic acid (5-HIAA)]were found to inhibit aldehyde-stimulated metabolism of glucose by the pentose phosphate shunt.

Receptors: Localization and Specificity of Binding of Serotonin in the Central Nervous System

Formation of a Schiff base between the ethylamine residue of serotonin and an appropriate carbonyl residue at the receptor site may be among the forces holding serotonin onto the receptor. Reduction of this imine may provide a means of permanently labeling receptors as a preliminary to their isolation.

Effect of reserpine on the incorporation in vivo of radioactivity from labeled serotonin and other 5-hydroxy-indole derivatives in mouse brain.

Abstract After endocranial-intraventricular administration of labeled serotonin or 5-hydroxy-indole-3-acetaldehyde into mice, radioactivity is incorporated into acid-insoluble material obtained from the brains of the animals. Under proper experimental conditions pretreatment with pargyline diminishes the incorporation from serotonin, but incorporation from the aldehyde level remains unaffected. Radioactivity due to acid-soluble metabolites obtained from the brain is higher after endocranial injection of serotonin into pargyline pretreated animals as compared to untreated controls. This effect is not observed after administration of the corresponding aldehyde. Pretreatment with reserpine greatly increases the radioactivity due to soluble metabolites in the acid washings and of the incorporation both at the serotonin and the aldehyde levels (endocranial administration). This effect may be observed over a wide range of dosages. In reserpine-pretreated animals, increased radioactivity in the washings is also observed after endocranial injection of a variety of other labeled compounds, including tryptamine, dl -norepinephrine, dopamine, l -lysine and 5-hydroxy-indole-3-acetic acid. The possible mechanism of this effect is discussed.

Effect of monoamine oxidase inhibitors on the labeling of subcellular fractions of brain and liver by 14C-serotonin☆

Abstract We recently observed that under certain conditions, radioactivity from labeled serotonin becomes firmly associated with acid-insoluble material obtained from mitochondrial preparations. This association is prevented by MAO-inhibitors 3 ( Alivisatos et al , 1966a ). A preliminary report of our observations on the mechanism and the potential significance of such associations is presented here.

Imidazolytic processes VI. Enzymic formation of benzimidazole and 5,6-dimethylbenzimidazole containing dinucleotides☆

Abstract The biosynthesis of benzimidazole and of 5,6-dimethylbenzimidazole dinucleotides from the corresponding free bases and diphosphopyridine nucleotide in the presence of a soluble, purified beef-spleen diphosphopyridine nucleotidase is reported. The properties of the new dinucleotides and of the benzimidazole mononucleotide are described. Problems connected with the configuration and the resistance to acid hydrolysis of the base-ribose bond in these dinucleotides are discussed.

Imidazolytic processes. V. Enzymically-catalyzed reactivity of certain imidazoles with coenzyme I.

Abstract In the DPN-DPNase system that catalyzes the (imidazolytic) breakdown of pyridine coenzymes, l -histidine and imidazoleacetic acid were found practically unreactive. The reactivity of the latter compound could be restored by esterification to imidazoleacetic acid ethylester. Imidazole, the parent compound of these heterocycles, and acetylhistamine exhibited normal reactivity. The dinucleotides (imidazolytic products) corresponding to the above compounds were isolated and their properties were studied.