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H Eyssen

Publications and source records attributed to H Eyssen.

At least 55 records · Page 3Linked to original sources
PubMed1980

Studies on the biosynthesis of isopenicillin N with a cell-free preparation of Penicillium chrysogenum.

When delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine was added to a cell-free system prepared by lysis of Penicillium chrysogenum protoplasts, "compounds X and Y" were detected after analysis on a cation-exchange column. The chromatographic position as well as results of experiments with double labelled tripeptides showed "compound X" to be the penicilloic acid of isopenicillin N. LLD-Tripeptide labelled with tritium at carbon-2 of th valine part was incorporated into isopenicillin N with retention of label. "Compound Y" retained all hydrogens on the valine part of the peptide, but lost half of the tritium on carbon-3 of the cysteine part. The results are consistent with the hypothesis that the LLD-tripeptide is converted into isopenicillin N via a monocyclic beta-lactam and without a dehydrovalinyl intermediate. Extensive transacylase activity was observed between isopenicillin N and 6-aminopenicillanic acid.

Biotransformation↗
PubMed1978

Stability of D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid in relation to its possible occurrence as a degradation product of penicillin by the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and the membrane-bound dd-carboxypeptidase from Bacillus stearothermophilus.

The stability of D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid has been studied under various conditions. In 10 mM cacodylate, pH 6.5, and at 55 degrees C, D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid (at concentrations lower than 1 mM) is hydrolyzed into N-formyl-D-penicillamine with a half-life of 3 to 4 min. On this basis, it is very unlikely that D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid could be one of the end products resulting from the cleavage of benzylpenicillin by the DD-carboxypeptidase of Bacillus stearothermophilus (as reported by Hammarström and Strominger (1976) J. Biol. Chem. 251, 7947--7949). In 3 mM phosphate, pH 7.5, and at 37 degrees C, D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid (at concentrations lower than 1 mM) has a half-life of 45 min. On the basis of kinetic experiments carried out under these conditions with phenoxymethylpenicillin and the DD-carboxypeptidase-transpeptidase of Streptomyces R61, it is concluded that the primary product which arises from the thiazolidine moiety of the antibiotic molecule and gives rise to N-formyl-D-penicillamine, has a half-life of 10 min, a value which is not compatible with the hypothesis that D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid would be an intermediate involved in the fragmentation pathway.

Acyltransferases↗
PubMed1977

Synthesis and characteristics of the specific monosulfates of chenodeoxycholate, deoxycholate and their taurine or glycine conjugates.

The isomeric monosulfates of chenodeoxycholate, deoxycholate, and their taurine or glycine conjugates, were synthesized and characterized. Reaction with chlorosulfonic acid in pyridine for 2 minutes mainly afforded the 3-monosulfates. To prepare the 7- or the 12-monosulfates, the 3-hydroxyl group was protected by carbethoxylation prior to sulfation of the 7- or 12-hydroxyl group for 24 h to 5 days; after sulfation, the protecting 3-carbethoxy function was removed by mild alkaline hydrolysis. The crude bile salt monosulfates were purified by chromatography on silica gel and on Sephadex LH-20 and were crystallized from methanolethanol-ethyl acetate. The results of elemental analysis demonstrated that the compounds were disodium dihydroxy bile salt monosulfates. Thin layer chromatography of the sulfates, and gas-liquid chromatography after oxidation and solvolysis, showed that the substances were pure and that the sulfate group was at the expected position.

Bile Acids and Salts↗
PubMed1976

Sulphated and unsulphated bile acids in serum, bile, and urine of patients with cholestasis.

Samples of serum, bile, and urine were collected simultaneously from patients with cholestasis of varying aetiology and from patients with cirrhosis; their bile acid composition was determined by gas/liquid chromatography and mass spectrometry. In cholestasis, the patterns in all three body fluids differed consistently and strikingly. In serum, cholic acid was the major bile acid and most bile acids (greater than 93%) were unsulphated, whereas, in urine, chenodeoxycholic was the major bile acid, and the majority of bile acids (greater than 60%) were sulphated. Secondary bile acids were virtually absent in bile, serum, and urine. The total amount of bile acids excreted for 24 hours correlated highly with the concentration of serum bile acids; in patients with complete obstruction, urinary excretion averaged 71-6 mg/24 h. In cirrhotic patients, serum bile acids were less raised, and chenodeoxycholic acid was the predominant acid. In healthy controls, serum bile acids were consistently richer in chenodeoxycholic acid than biliary bile acids, and no bile acids were present in urine. No unusual monohydroxy bile acids were present in patients with primary biliary cirrhosis, but, in several patients, there was a considerable amount of hyocholic acid present in the urinary bile acids. The analyses of individual bile acids in serum and urine did not appear to provide helpful information in the differential diagnosis of cholestasis. Thus, in cholestasis, conjugation of chenodeoxycholic acid with sulphate becomes a major biochemical pathway, urine becomes a major route of bile acid excretion, and abnormal bile acids are formed.

Bile↗
PubMed1976

Incorporation of double-labelled valine into delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine by Penicillium chrysogenum.

The incorporation of valine into the LLD-tripeptide, delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine, a precursor of penicillin, was studied by incubating mycelial mats of Penicillium chrysogenum Wis. 49-2105 with double labelled valines. L-valine was incorporated into the LLD-tripeptide without formation of an alpha, beta-didehydrovaline intermediate. Intact D-valine was not incorporated into the LLD-tripeptide.

Carbon Radioisotopes↗
PubMed1976

Synthesis of (beta-methyl-3H-)-benzylpenicillin and (beta-methyl-3H)-6-aminopenicillanic acid.

The synthesis of benzylpenicillin and 6-aminopenicillanic acid, labeled with tritium in the beta-methyl group, is described. Benzylpenicillin S-sulfoxide benzyl ester is refluxed in benzene and tritiated water and is successively debenzylated and deoxygenated to (beta-methyl-3H)-benzylpenicillin. Removal of the side chain with a bacterial acylase gives (beta-methyl-3H)-6-aminopenicillanic acid.

Escherichia coli↗
PubMed1975

Synthesis of the specific monosulfates of cholic acid.

The three isomeric cholic acid-monosulfates were synthetized and characterized. Cholic acid-3-sulfate was obtained by reacting cholic acid for 2 min with chlorosulfonic acid in pyridine and chromatography of the resulting bile salt mixture on Sephadex LH-20. The 7- and the 12-monosulfate were prepared by sulfation of the corresponding monohydroxy-diacetates followed by removal of the acetyl groups by alkaline hydrolysis and purification by chromatography on Sephadex LH-20. On TLC in n-butanol-acetic acid-water (10:1:1, v/v) the Rf values were 0.59 for cholic acid-3-sulfate, 0.52 for cholic acid-7-sulfate and 0.48 for cholic acid-12-sulfate. The time required for complete solvolysis at 37 degrees C in acid methanol-acetone (1:9) was 3 h for cholic acid-3-sulfate, 12 h for the 12-monosulfate and 18 h for the 7-monosulfate.

Cholic Acids↗
PubMed1975

Incorporation of double-labeled L-cystine and DL-valine in penicillin.

l-[3,3'-(3)H]cystine was incorporated into penicillin with retention of one tritium. This result can be explained by beta-lactam formation through ring closure between C3 of cysteine and NH of valine. No radioactivity of dl-[2,3-(3)H]valine was incorporated into penicillin. The loss of isotope at C2 occurs during the inversion of configuration. The loss of label at C3 is discussed in terms of possible intermediates for the formation of the thiazolidine ring of penicillin.

Carbon Radioisotopes↗
PubMed1975

Presence of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine in fermentations of Penicillium chrysogenum.

Cultures of Penicillium chrysogenum, growth with [(35)S]sulfate or labeled amino acids, were examined by ion-exchange chromatography for possible peptidic precursors of penicillin. A sulfur-containing compound, present in both the mycelial extracts and the culture filtrates, was eluted at the location of the synthetic lld-tripeptide delta-(l-alpha-aminoadipyl)-l-cysteinyl-d-valine. Since this compound was also labeled when the cultures were incubated with dl-[6-(14)C]alpha-aminoadipic acid, l-[3,3'-(3)H]cystine, or dl-[1-(14)C]valine, its identity with the synthetic lld-tripeptide can be accepted. No delta-(l-alpha-aminoadipyl)-l-cysteine or lll-tripeptide were detected. The implications of these findings for tripeptide and penicillin biosynthesis are discussed.

Culture Media↗