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Biomedical subjects

G Heckmann

Publications and source records attributed to G Heckmann.

10 recordsLinked to original sources
PubMed1982

Biosynthesis of vitamin B12 in anaerobic bacteria. Mode of incorporation of glycine into the 5,6-dimethylbenzimidazole moiety in Eubacterium limosum.

[1-13C]Glycine, [2-13C]glycine, and [15N]glycine were added to fermentations with the strictly anaerobic vitamin B12 producer Eubacterium limosum. The vitamin B12 isolated was almost exclusively labeled in its 5,6-dimethylbenzimidazole moiety. It was methylated and degraded to 1,5,6-trimethylbenzimidazole. The position of the 13C label was determined from the 13 C NMR spectrum using the natural-abundance 13C NMR spectrum of 1,5,6-trimethylbenzimidazole as reference. Thus it was found that C-1 of glycine is incorporated into position 7a, C-2 of glycine into position 3a of the 5,6-dimethylbenzimidazole moiety of vitamin B12. In order to show whether the nitrogen atom of glycine is also incorporated, the vitamin B12 from the experiment with [15N]glycine was degraded to 5,6-dimethylbenzimidazole. The 1H NMR spectrum of this compound exhibited in the region of the C-2 proton a doublet from the 15N-labeled part of the molecules (35%) and a singlet from the unlabeled molecules. This doublet indicates that only one of the two nitrogen atoms of 5,6-dimethylbenzimidazole is labeled. From the incorporation pattern of 13C-labeled glycine it must be deduced that this is N-3 of the 5,6-dimethylbenzimidazole moiety of vitamin B12. These experiments reveal that one molecule of glycine is incorporated into 5,6-dimethylbenzimidazole moiety of vitamin B12 in a regiospecific manner.

Benzimidazoles↗
PubMed1980

Biosynthesis of vitamin B12. Experiments with the anaerobe Eubacterium limosum and some labelled substrates.

1. The anaerobic microorganism Eubacterium limosum (DSM 20 402), grown in the presence of L-[methyl-14C]methionine, produces vitamin B12 not only labeled in the corrin ring, but also in the 5,6-dimethylbenzimidazole moiety. The vitamin B12 obtained in a similar experiment with L-[methyl-13C]methionine showed nine signals in the 13CV NMR spectrum. Seven of these signals are due to the seven 'extra' methyl groups of the corrin ring, two signals originate from the two methyl groups of the 5,6-dimethylbenzimidazole moiety. This result is in contrast to previous experiments with aerobic and aerotolerant organisms, where L-methionine is only the precursor of the seven corrin methyl groups, and the 5,6-dimethylbenzimidazole is formed from riboflavin. 2. E. limosum transforms exogenously added benzimidazole into benzimidazolylcobamide, but with [2-14C]benzimidazole it was shown that benzimidazole is not a precursor of the 5,6-dimethylbenzimidazole moiety of vitamin B12. 3. Radioactivity from [2-14C]glycine is almost exclusively incorporated into the 5,6-dimethylbenzimidazole moiety of vitamin B12, but not into the corrin moiety. This demonstrates that in E. limosum delta-aminolevulinic acid, the precursor of the corrin moiety, is not formed as in many other organisms from succinyl-CoA and glycine.

Anaerobiosis↗
PubMed1978

[Biochemistry and clinical significance of oral exocrine pancreatic function test by means of fluoresceinedilaurate (author's transl)].

Column chromatography of extracts and secretions of the pancreas as well as of sera from patients suffering from inflammations of this organ yields three esterases different from each other in molecular size. These enzymes could be shown to be not identical with lipase. They may be classified as aryl-esterases considering their activities in hydrolyzing synthetic substrates such as esters of fluoresceine with fatty acids. Fluoresceinedilaurate, therefore, proved to be very advantageous in an orally performed test of exocrine pancreatic function. Healthy persons show in this procedure relative excretion of fluoresceine during ten hours of 66.3 +/- 30.4%, patients suffering from pancreatic diseases only 12.7 +/- 9.8% of the dye.

Esterases↗