A novel pathway for the synthesis of solanidine in the isolated chloroplast from greening potatoes.

Synthesis of chlorophyll always preceded the synthesis of solanine in cold-stored potatoes in the presence of dim light (30--40 lux). Isolated chloroplasts from green peelings were able to fix CO2. The evidence obtained showed a direct reduction of CO2 to formate, which was the primary product of fixation. Apart from this the chloroplasts were capable of incorporating NaH14CO3, [14C]formate, [2-14/C]glycine, [2-14C]pyruvate, [2-14C]acetate, [2-14C]mevalonate and [U-14C]serine into the solanidine moiety of the alkaloid. The intermediates in the pathway between CO2 and acetate have been identified as formate, glycine, serine and pyruvate. The localization of the enzymes involved in the reaction sequence viz. serine hydroxymethyl-transferase, and pyruvic dehydrogenase complex, in the isolated chloroplast has been established.