Synthèse des protéines dans les pupes de Sphinx ligustri.

peer reviewedAT the beginning of the pupal stage of Sphinx ligustri, a lysis of larval tissues occurs. In winter, during diapause, the pupa is a bag full of blood containing a suspension of partially broken down larval tissues. In spring, diapause is broken, formation of adult tissues is speeded up and the moth becomes rapidly ready to emerge. Most of the amino-acids used for adult protein synthesis come from larval tissues; the question is whether the larval proteins are hydrolysed to free amino-acids before being used for adult protein synthesis, or whether adult proteins are built up from larger units that might be carried by phagocytes which are known to destroy the larval tissues. In order to approach an answer to this question, we decided to compare the mean specific rates of protein synthesis (rate of synthesis/amount of proteins) from one free amino-acid, namely glycine, in Sphinx ligustri pupæ, either in diapause or at the moment of the development of the adult organs. © 1957 Nature Publishing Group

Metabolism of carnitine and crotonic betaine in the chick embryo.

peer reviewe

The use of thioglycolate to distinguish between 3' AP (apurinic/apyrimidinic) endonucleases and AP lyases.

Addition of thioglycolate and DEAE-Sephadex chromatography were used to analyze the cleavage of the C(3')-O-P bond 3' to AP (apurinic/apyrimidinic) sites in DNA and to distinguish between a mechanism of hydrolysis (which would allow the nicking enzyme to be called 3' AP endonuclease) or beta-elimination (so that the nicking enzyme should be called AP lyase). For this purpose, DNA labelled in the AP sites was first cleaved by rat-liver AP endonuclease, then with the 3' nicking catalyst in the presence of thioglycolate and the reaction products were analyzed on DEAE-Sephadex: deoxyribose-5-phosphate (indicating a 3' cleavage by hydrolysis) and the thioglycolate:unsaturated sugar-5-phosphate adduct (indicating a cleavage by beta-elimination) are well separated allowing to eventually easily discard the hypothesis of a hydrolytic process and the appellation of 3' AP endonuclease. We have shown that addition of thioglycolate to the unsaturated sugar resulting from nicking the C(3')-O-P bond 3' to AP sites by beta-elimination is an irreversible reaction. We have also shown that the thioglycolate must be present from the beginning of the reaction with the nicking catalyst to prevent the primary 5' product of the beta-elimination reaction from undergoing other modifications that complicate the interpretation of the results

Use by Bombyx mori of the carboxyl group of L-phenylalanine for the synthesis of silk amino acids

peer reviewe

Contributions à la biochimie du ver à soie. XXX. Biosynthèse de tréhalose et de glycogène à partir de glucose-1-phosphate

1. When injected into silkworms in the middle of the fifth larval instar, labelled G-1-P is principally used for the synthesis of hemolymph trehalose. 2. Glycogen synthesis from the same source in the fat body proceeds more rapidly in undernourished larvae than in those fed normally. 3. Owing to the poor incorporation of the radioactivity in the glycogen and especially in the trehalose of the fat body, it is suggested that the trehalose could be synthesized from pyruvate elsewhere than in the fat body, and that the biosynthetic pathway of trehalose from pyruvate does not necessarily pass through glycogen. 4. The synthesis of trehalose and glycogen, as well as the hydrolysis of glycogen, could be controlled, directly or indirectly, by the variations of the trehalose level in the hemolymph. 5. The gluconeogenetic pathways in the silkworm are discussed and presented in the form of a partially hypothetical figure.Le G-1P marqué, injecté à des Vers à soie au milieu du 5e âge larvaire, est principalement utilisé pour la synthèse du tréhalose de l'hémolymphe. La synthèse de glycogène au sein du tissu adipeux est beaucoup moins rapide chez les chenilles sous-alimentées que chez les chenilles normalement nourries. La faible incorporation de radioactivité dans le glycogène et surtout dans le tréhalose du tissu adipeux suggère que le tréhalose peut être synthétisé ailleurs que dans le tissu adipeux et que la voie biosynthétique du tréhalose à partir du pyruvate ne passe pas nécessairement par le glycogène. Les vitesses relatives de synthèse du glycogène et du tréhalose, de même que la dégradation du glycogène pourraient être contrôlées, directement ou indirectement, par les variations du niveau de la tréhalosémie. Les voies de la gluconéogenèse chez le Ver à soie sont résumées en un schéma partiellement hypothétique