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A reversible chemical modification of the tryptophan residue

Abstract Tryptophan and tryptophan-containing peptides and proteins specifically react in formic acid-hydrochloric acid solutions giving the corresponding 1-formyltryptophan derivatives which can successively be deformylated in mild conditions. The reactions are proposed for a reversible modification of tryptophan residues. A tentative of tryptophan analysis in proteins is reported and other possible applications are discussed.

Solid phase sequential analysis: Specific linking of acidic peptides by their carboxyl ends to insoluble resins

The success of methods such as the Edman degradation for solid-phase sequential analysis of peptides depends on having efficient methods for attaching peptides to insoluble resins before degradation. Previously described [2,3] attachment procedures using carbonyldiimidazole to couple the C-terminal carboxyl to an amino resin, suffer from the serious problem that side-chain carboxyls also become activated, leading to side reactions. In order to make the solid-phase Edman degradation generally applicable, it is essential to have a procedure for selective activation of the C-terminal carboxyl groups. We wish to report here that a.iV,N’-disubstituted carbodiimide can effect both protection of side-chain carboxyl groups and activation of the C-terminal under suitable experimental conditions (scheme A).

Alumina-phosphate complexes for immobilization of biomolecules

Organic compounds containing the -PO3H2 function are strongly and specifically adsorbed by aluminum oxide in water within a large range of pH. The reversible character of the interaction allows the adsorbed organic phosphates to be displaced by inorganic phosphate buffers resulting in their purification by an affinity-like chromatographic procedure. The interaction between alumina and selected multifunctional compounds containing a phosphonate group yields a chemically activated alumina-phosphate complex onto which enzymes or other molecules can be immobilized. A number of proteases immobilized on alumina through such phosphate interactions proved to be active in the presence of organic solvents. As a consequence, enzyme-catalyzed peptide synthesis in a water-limited environment and optical resolution of amino acids in water-organic solvent emulsions can be accomplished.

Des structures simples aux potentialités pharmacologiques élevées: les β carbolines. Origines, synthèses, propriétés biologiques

We reviewed the origins, the synthetic pathways and the biological properties of beta-carbolines, the condensation products of tryptophan and indole alkylamines with aldehydes. They were found in many plants, some of which have been used as hallucinogens. They also occur as minor constituents in tobacco smoke. In mammalian body, beta-carboline derivatives occur normally in plasma, platelets and urine, moreover it seems that some are formed in human body after alcohol intake. Due to interesting biological effects described in recent years (inhibition of monoamine oxidase, binding to benzodiazepine receptors, comutagenic and carcinogenic properties, 5-hydroxy tryptamine uptake inhibition), many attempts were made to prepare beta-carbolines starting from various indole derivatives. We reviewed the published methods up to 1975 and summarized the main patents related with pharmacological properties of synthetic beta-carbolines.

Purification and substrate characterization of a human enkephalin-degrading aminopeptidase

A 5000-fold purification of the enzyme responsible for the rapid inactivation of enkephalin in human blood has been achieved: this enzyme cleaves the N-terminal tyrosine from enkephalin and from short peptides provided their first amino acid is aromatic. The enzyme, an enkephalin-degrading aminopeptidase (alpha-aminoacyl-peptide hydrolase, EC 3.4.11.11), requires a free amino group on the substrate and has a maximum activity around pH 8. Its appearance molecular weight is in the range of 80 000-90 000 and an apparent Michaelis constant of 0.4 mM was determined.

Amino acid hydroxamates as inhibitors of the human enkephalin-degrading aminopeptidase

Abstract Amino acid hydroxamate derivatives inhibit the recently characterized enkephalin-degrading aminopeptidase from human blood (α-aminoacyl-peptide hydrolase, EC 3.4.11.11). The efficiency of inhibition depends on the structure of the amino acid hydroxamate employed. Amino acid hydroxamate decivatives also inhibit metalloendopeptidases and enkephalin-degrading enzymes from rat brain. The degradation of enkephalin in blood and in the brain seems to be under the control of a number of metallopeptidases: suitable amino acid hydroxamate derivatives can therefore be proposed as general inhibitors of enkephalin breakdown.

Immobilization of Enzymes on Alumina by Means of Pyridoxal 5'-Phosphate

A number of proteases have been immobilized on alumina in a two-step procedure: the first step converted them into semisynthetic phosphoproteins which, in the second step, spontaneously bonded to alumina through their phosphate function. The immobilized enzymes thus obtained showed the physical properties typical of the inorganic carrier and a high activity on low molecular weight substrates.

Specific sulfonation of tyrosine, tryptophan and hydroxy-amino acids in peptides

1. ClSO3H in trifluoroacetic acid rapidly converts serine and threonine into O-sulfate ester derivatives while tyrosine and tryptophan are converted into arylsulfonic acids. 2. H2SO4 in trifluoroacetic acid reacts more slowly with serine, threonine and tyrosine while is not able to modify tryptophan. 3. All other amino acids are perfectly stable under the above reaction conditions. 4. Peptides containing susceptible amino acid residues are specifically converted into the corresponding sulfonated derivatives in high or quantitative yield.

Specific O-acylation of hydroxylamino acids in presence of free amino groups

Abstract Serine, threonine and tyrosine hydroxyl groups are readily acylated by carboylic acid chlorides in anhydrous trifluoroacetic acid while the free amino groups are completely stable in the same reaction conditions. The usefulness of this O-acylation reaction for specific protein modifications as well as for synthetic and analytical purposes is discussed.

Selective retention of organic phosphate esters and phosphonates on aluminium oxide

Compounds containing the −PO3H2 function, such as monoesters of phosphoric acid and phosphonic acids, specifically bind to aluminium oxide in aqueous solution under experimental conditions where non-phosphorylated compounds are completely desorbed. The bound organic phosphate can be specifically displaced by aqueous solution of inorganic phosphates thus allowing their separation or detection by a technique similar to that of affinity chromatography. The consequences of this finding for phosphate compound biochemistry are discussed.