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Biomedical subjects

K Decker

Publications and source records attributed to K Decker.

At least 199 records · Page 11Linked to original sources
PubMed1979

Comparative metabolic studies on liver sinusoidal cells and different types of macrophages.

Sinusoidal cells of rat liver, rat peritoneal macrophages and rabbit alveolar macrophages were checked for their viability and compared with regard to cell weight, protein and DNA content. Glycogen was virtually absent from sinusoidal cells and peritoneal macrophages; alveolar macrophages contained glycogen whose level increased after activation by Freund's adjuvant and decreased during phagocytosis in the absence of glucose. Of the different nucleotides assayed, UDPglucose levels were low in the nonglycogen-forming cells, but quite high in alveolar macrophages. The capacity to metabolize galactose is much smaller in all cell types investigated than in hepatocytes.

Animals↗
PubMed1978

Regulation of flavoprotein synthesis studied in vivo in a riboflavin-requiring mutant of Arthrobacter oxidans.

The biosynthesis of two flavoproteins, 6-hydroxy-D-nicotine oxidase with covalently bound FAD and 6-hydroxy-L-nicotine oxidase containing non-covalently bound FAD, was studied in wild-type cells and in a riboflavin-requiring mutant of Arthrobacter oxidans. In the mutant cells, the rate of synthesis and the maximal activity level of both enzymes after induction by nicotine depended on the amount of added riboflavin. The low rate of synthesis in the presence of 2 micron riboflavin could be enhanced during the induction phase by further addition of riboflavin (33 micron). Inhibitors of translation (chloramphenicol or streptomycin) completely blocked the synthesis of both flavoproteins. Inhibitors of transcription (rifamycin S or actinomycin D) stopped the synthesis of both enantiozymes in wild-type cells and in the mutant grown in the presence of a saturating supply of riboflavin (15 micron). Under conditions of restricted flavoprotein synthesis (2 micron riboflavin in the medium), however, the mutant cells continued to synthesize the enzyme for 2--3 h after the addition of the transcription inhibitors. It appears, that in these cells a rather stable m-RNA accumulated during riboflavin-limited flavoprotein synthesis. The dependence of the effect of transcription inhibitors on the extracellular supply of riboflavin suggests that the regulation of the synthesis of both flavoproteins occurs not only by control of gene expression (induction by nicotine), but also at the level of translation through the availability of FAD.

Arthrobacter↗
PubMed1978

FAD is covalently attached to peptidyl-tRNA during cell-free synthesis of 6-hydroxy-D-nicotine oxidase.

The process, by which FAD is attached covalently to the 6-hydroxy-D-nicotine oxidase apoprotein in D-nicotine-induced cells of Arthrobacter oxidans was studied in vitro. [3H]Adenine-labelled FAD prepared biosynthetically in Clostridium kluyveri was incorporated into the 6-hydroxy-D-nicotine oxidase molecule during cell-free translation. FAD rather than FMN or riboflavin was thus shown to be the flavin derivative transferred to the polypeptide chain. After short-term protein synthesis on ribosomes from induced A. oxidans cells in the presence of an Escherichia coli MRE 600 supernatant fraction and [adenine-2-3H]FAD, THE PEPTIDYL-TRNA fraction was separated from completed polypeptides. Labelled FAD was found to be covalently attached to the tRNA-bound polypeptides. Cleavage of the tRNA-peptide bond released labelled polypeptides the largest of which migrated as authentic 6-hydroxy-D-nicotine oxidase during dodecylsulfate/polyacrylamide gel electrophoresis. These results strongly suggest that FAD is incorporated into the nascent polypeptide chains of 6-hydroxy-D-nicotine oxidase during ribosomal translation.

Adenine↗