STABLE ISOTOPES IN BIOCHEMICAL STUDIES

To define where the borderline between biochemistry and medicinal chemistry occurs is an invidious task. So far as the medicinal chemist is concerned, the 

Carbon-13 labelling has been utilised in studies of valine metabolism. [3- C]-Valine was administered to fasted rats and the glycogen formed was isolated degradation confirmed the formation of a 3-carbon intermediate [175], A patient with methylmalonic acidemia has been studied by administration of [2- CJvaline and [2,3- C]valine methylmalonic acid was isolated from the urine and analysed by C-NMR [176,177]. 

The value of bile acids labelled with carbon-13 in gastroenterological research has been critically evaluated and compared with radioactive tagging. Stable iso- 

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]. 

Mass spectra, C-NMR, and N-NMR have been applied to the study of iso-topically labelled compounds of haematological interest. C, RN-labelled haemoglobins, N-labelled protoporphyrin-IX and coproporphyrin-III, and RC-and N-labelled globins have been investigated [134], 

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