. Ciba Foundation conferences on istopes in biochemistry;. Radioactive tracers in biochemistry; Isotopes -- Physiological effect. Biosynthesis of Porphyrins 61 in both carboxyl groups would on decarboxylation yield a succinyl derivative labelled only in the carboxyl group. This compound in turn would be converted to succinic acid, a symmetrical compound. If the latter reaction is reversible (XOC-CHs-CHsCOOH^HOOC-CHa-CHs-COOH) the succinyl derivative arising from the symmetrical succinate would contain equal activity in the carboxyl group and in the other terminal carbon atom. However, since th
. Ciba Foundation conferences on istopes in biochemistry;. Radioactive tracers in biochemistry; Isotopes -- Physiological effect. Biosynthesis of Porphyrins 61 in both carboxyl groups would on decarboxylation yield a succinyl derivative labelled only in the carboxyl group. This compound in turn would be converted to succinic acid, a symmetrical compound. If the latter reaction is reversible (XOC-CHs-CHsCOOH^HOOC-CHa-CHs-COOH) the succinyl derivative arising from the symmetrical succinate would contain equal activity in the carboxyl group and in the other terminal carbon atom. However, since the succinyl derivative 14 C OOH I CHo I CH2 C = 0 I COOH 14 C^OOH. C"*OOH C'^OOH I CH? 1 CHp I COX C"^00H CH2 CH2 ' 14 c'^ox. / PYRROLES Fig. 6. Formation of succinyl derivative and distribution of ^*C in this compound in experiment using carboxyl labelled acetate. is presumably formed more extensively from a-ketoglutarate than it is from succinate, the carboxyl group of the pooled intermediate arising from both processes would contain more activity than the other terminal carbon atoms.* Two molecules ?According to the formulation of the functioning of the tricarboxylic cycle in porphyrin formation, carboxyl labelled succinate cannot give rise to labelled haem unless this reaction occurs. It has recently been found by Shemin and Kumin that carboxyl labelled succinate produced labelled haem in which pyrrole Rings A and B contained 40 per cent of the activity and Rings C and D contained 60 per cent. The carboxyl group of Rings C and D contained one- third of the activity of these rings. This distribution agrees with the theory and therefore further supports the above reaction and the utilization of a four carbon compound for porphyrin Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ciba Fo
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