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Biomedical subjects

B Hodgson

Publications and source records attributed to B Hodgson.

27 records · Page 2Linked to original sources
PubMed1972

The use of acid alumina and sephadex LH-20 for the separation and characterization of ethanol-soluble peptides produced by Bacillus brevis.

Cell extracts from Bacillus brevis (A.T.C.C. 10068), grown with various media, incorporated certain (14)C-labelled amino acids that are normally components of tyrothricin into material that was extracted by ethanol from the precipitate formed by adding acid. When this material was separated by paper and silica-gel thin-layer chromatography and paper electrophoresis (14)C was located in those regions that also contained gramicidin and tyrocidine. From a study of the properties of the system responsible for the incorporation it was deduced that non-tyrothricin materials were present. It was shown that the methods normally used to characterize tyrothricin do not adequately distinguish between tyrothricin and non-tyrothricin materials. However, a method for separating these materials was devised. This involved elution with ethanol from columns of acid alumina followed by gel filtration on Sephadex LH-20 with dimethylformamide-water solvent. The behaviour of gramicidin and tyrocidine on the Sephadex LH-20 column was examined, and it was concluded that the separation was not caused simply by gel filtration of unassociated molecules. Also, tyrocidine molecules with different amino acid compositions seemed to have different affinities for the Sephadex LH-20 column.

Aluminum↗
PubMed1968

A direct pathway for the conversion of propionate into pyruvate in Moraxella lwoffi.

1. The identity of the organism previously known as Vibrio O1 (N.C.I.B. 8250) with a species of Moraxella is established. 2. The ability of cells to oxidize propionate is present only in cells with an endogenous respiration and this ability is increased 80-fold when the organism is grown with propionate. 3. Isocitrate lyase activity in extracts from propionate-grown cells is the same as that in extracts from lactate-grown cells, about tenfold greater than that in extracts from succinate-grown cells and slightly greater than half the activity in extracts from acetate-grown cells. 4. With arsenite as an inhibitor conditions were found in which the organism would catalyse the quantitative oxidation of propionate to pyruvate. When propionate was completely utilized pyruvate was metabolized further to 2-oxoglutarate. 5. The oxidation of propionate by cells was incomplete both in a ;closed system' with alkali to trap respiratory carbon dioxide and in an ;open system' with an atmosphere of oxygen+carbon dioxide (95:5). Acetate accumulated. Under these conditions [2-(14)C]- and [3-(14)C]-propionate gave rise to [(14)C]acetate. The rate of conversion of [2-(14)C]propionate into (14)CO(2), although much less than the rate of conversion of [1-(14)C]propionate into (14)CO(2), was slightly greater than the rate of conversion of [3-(14)C]propionate into (14)CO(2). 6. The oxidation of propionate by cells was complete in an ;open system' with an atmosphere of either oxygen or air. Under these conditions very little [1-(14)C]propionate was converted into (14)C-labelled cell material. The conversion of [2-(14)C]- and [3-(14)C]-propionate into (14)C-labelled cell material occurred at an appreciable rate, the rate for the incorporation of [3-(14)C]propionate being slightly more rapid. In the absence of a utilizable nitrogen source part of the [(14)C]propionate was incorporated into some reserve material, which was oxidized when added substrate had been completely utilized. 7. [(14)C]-Pyruvate produced from [(14)C]propionate was chemically degraded. The C((1)) of propionate was found only in C((1)) of pyruvate. At least 86% of C((2)) of pyruvate was derived from C((2)) of propionate and at least 92% of C((3)) of pyruvate from C((3)) of propionate. 8. These results are incompatible with the operation of any of the previously described pathways for propionate metabolism except the direct one, perhaps via an activated acrylate.

Carbon Dioxide↗
PubMed1968

A direct pathway for the metabolism of propionate in cell extracts from Moraxella lwoffi.

1. Extracts from Moraxella lwoffi oxidize propionate, but at a low rate when compared with whole cells. 2. This oxidative activity requires the formation of propionyl-CoA. 3. Enzymes catalysing the formation of propionyl phosphate and propionyl-CoA are present. The presence of a propionyl-CoA hydrolase is considered to be an artifact, but partly responsible for the low rates of oxidation. 4. Enzymes catalysing the reduction of NAD(+) and the formation of pyruvate with propionyl-CoA as substrate are also present. 5. That the only pathway for the metabolism of propionate in extracts is a direct one to acetate via pyruvate was confirmed by the use of (14)C-labelled materials. 6. A possible sequence of enzyme-catalysed reactions that will account for the experimental observations is described.

Acetates↗