Biomedical subjects

L Ettlinger

Publications and source records attributed to L Ettlinger.

At least 19 recordsLinked to original sources

PubMed1982

Secretion of tyrosinase in Streptomyces glaucescens.

In Streptomyces glaucescens, the intracellular and the extracellular enzyme forms of tyrosinase were found to be indentical in molecular weight (29 000), in copper content (0.21%), in the 19 amino acids at the amino-terminal end and in the ratio of cresolase to catecholase activity (0,005). The tyrosinase secretion process exhibited a constant rate of 0.15 units h-1 (mg protein)-1. Under highly induced conditions intracellular tyrosinase was accumulated. Mutations responsible for the non-melanogenic, tyrosinase-positive non-secretor mutant type are located chromosomally on the upper right arc of the S. glaucescens map near the ade-1 marker.

Catechol Oxidase↗

PubMed1980

A new rearrangement reaction in tyrosine metabolism.

Human faecal specimens were incubated under anaerobic conditions with several dideuterated tyrosine metabolites. 3-(4-Hydroxy[3,5-2H2]phenyl)propionic acid and 3-(4-hydroxy[3,5-2H2]phenyl)lactic acid yielded the rearrangment product 3-(3-hydroxy[2,4-2H2]phenyl)propionic acid. The starting materials as well as the product all contained two deuterium atoms both ortho to the hydroxyl group. Therefore the rearrangement reaction must depend on a shift of the side chain.

Chemical Phenomena↗

PubMed1977

Glucose metabolism in Acetobacter aceti.

Acetobacter aceti NCIB 8554 grows on a minimal medium with ethanol but not with glucose as carbon and energy source. Addition of glucose to a wild type culture on ethanol has no influence on growth of the organism. Growth of a glucose sensitive mutant A5 is inhibited by the addition of glucose until all glucose has disappeared from the medium. In order to determine the routes by which glucose is metabolised in wild type and mutant, radiorespirometric, enzymatic, and uptake experiments have been performed. For the radiorespirometric experiments of the "continuous substrate feeding" type as apparatus has been constructed. Of the glucose entering the cells about 30% is excreted as gluconate and 6% metabolised with liberation of C-1 as CO2. The rest is accumulated intracellularly. No differences were found between wild type and mutant. Under different growth conditions and with different enzymatic assay methods no pyruvate kinase activity (EC 2.7.1.40) could be detected. This might explain the inability of A. aceti to grow on glucose.

Acetobacter↗

PubMed1976

Characterization of the acetyl-CoA synthetase of Acetobacter aceti.

The acetate activating system of Acetobacter aceti has been studied. The enzyme responsible, acetyl-CoA synthetase, has been purified about 500-fold from crude cell extracts and was approximately 85% pure as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. The purified enzyme showed optimal activity at pH 7.6 in both Tris-HCL and potassium phosphate buffers. In its purest form, the enzyme was stable at 4 degrees-C but denatured upon freezing. The Km values for CoA, ATP and acetate were found to be 0.104 mM, 0.36 mM and 0.25 mM respectively; propionate and acrylate were also activated by the enzyme but not butyrate, isobutyrate or valerate. GTP, UTP, CTP and ADP could not replace ATP in the reaction, and cysteine or pantetheine failed to replace CoA. The cationic requirements were studied and of the divalent cations tested, only Mn2+ could significantly replace Mg2+ in the reaction; K+ and NH4+ stimulated enzyme activity but inhibited at high concentrations; Na+ was a poor activator, but did not inhibit at higher concentrations. The effect of a number of glucose and other metabolites on enzyme activity has been tested.

Acetate-CoA Ligase↗

PubMed1976

Study of the intestinal tyrosine metabolism using stable isotopes and gas chromatography-mass spectrometry.

Deuterated tyrosine, 4-hydroxyphenyllactic acid, 4-hydroxyphenylpropionic acid, 4-hydroxyphenylacetic acid and 4-hydroxybenzoic acid were incubated under anaerobic conditions with human faecal specimens for the in vitro study of their respective metabolisms. After 1 week, aromatic acids and phenols were extracted and analyzed by gas chromatography-mass spectrometry. [3',5'-2H2]Tyrosine produced 4-hydroxyphenyllactic acid, 4-hydroxyphenylpropionic acid and 4-hydroxyphenylacetic acid; [3',5'-2H2]-4'-hydroxyphenyllactic acid produced 4-hydroxyphenylpropionic acid, 3-hydroxyphenylpropionic acid, 4-hydroxyphenylacetic acid and phenylproionic acid; [3',5'-2H2]-4'-hydroxyphenyl-propionic acid produced 3-hydroxyphenylpropionic acid and phenylpropionic acid; [3',5',2,2-2H4]-4'-Hydroxyphenylacetic acid produced p-cresol; and [3',5'-2H2]-4'-hydroxybenzoic acid produced phenol. Thus the intestinal flora showed activities for decarboxylation leading to phenol and p-cresol, dehydroxylation leading to phenylpropionic acid and rearrangement leading to 3-hydroxyphenylpropionic acid. Rentention of both deuterium labels was observed in the rearrangement reaction.

Anaerobiosis↗

PubMed1975

Regulation of aspartokinase and homoserine dehydrogenase in acetic acid bacteria.

The regulation of aspartokinase and homoserine dehydrogenase has been studied in three Acetobacter and two Gluconobacter species. Both enzymes were regulated by feedback inhibition. Aspartokinase was inhibited by L-threonine and concertedly inhibited by L-threonine plus L-lysine. The homoserine dehydrogenase was NADP-specific and was inhibited by L-threonine. Separation of the two enzymes by ammonium sulphate fractionation was possible in Acetobacter peroxydans, A. rancens and Gluconobacter melanogenus but not in A. liquefaciens or G. oxydans.

Acetobacter↗

PubMed1974