Amino acid dependent exchange between pyrophosphate and adenosine triphosphate in spinach preparations.

Chloroplasts have been considered primarily as the site of light-catalyzed CO2 fixation and photosynthetic phosphorylation. The present investigation was initiated in order to obtain further information on the question of protein synthesis as an integral function of chloroplasts. Towards this end a study was made of the activation of amino acids, a reaction generally regarded as the first step in protein synthesis (l-3). With the finding, as will be shown, that chloroplasts contain a separate system of amino acid activation, comparative studies were made with spinach cytoplasm. After this work was completed, a similar but more limited study was reported by Clark (4).