Positional enrichment, carbon labeling experiments

The enrichment of die C20- and C22-polyenoic acids of this type should be achieved by feeding appreciable amounts of the aII-cis-A i-Ci8-die-noic acid, a positional isomer of linoleic acid with the double bonds shifted one carbon atom toward the carboxy group. This acid, obtained by total synthesis and C -labeled at carbon atom 13, has been administered to animals (13a). In this experiment we expected the enrichment of the arachidonic acid isomer, A - -C2o-tetraenoic acid. The results. 

The enzyme Candida utilis 6-phosphogluconate dehydrogenase with carbon-13 enriched to 90 atom% has been obtained by growing the yeast with Relabelled acetic acid as the sole carbon source [186]. Carbon-13 composition had very little, if any, effect on the catalytic properties of the enzyme. Sodium [ RC]lactate has been used to study the conversion of lactate to liver glycogen in the rat. Lactate labelled with C at position 2 and C at position 3 was also used. Carbon-13 was measured by mass spectrometry [187]. Similar experiments were carried out with RC-labelled propionate and C- and C-labelled propionate [188]. 

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