Compartmentation of terpenoid biosynthesis in green plants. A proposed route of acetyl-coenzyme A synthesis in maize chloroplasts.

On the basis of radioisotope-incorporation experiments it is suggested that acetyl-CoA, an obligatory intermediate in chloroplast terpenoid biosynthesis, may be formed in maize from photosynthetically fixed carbon dioxide by the route carbon dioxide-->glycollate-->glyoxylate-->glycine-->serine-->pyruvate-->acetyl-CoA. The proposed route is supported by conventional radioisotope-dilution studies and by experiments with inhibitors affecting reactions involved in the pathway. The proposed route appears to play little part in formation of extrachloroplastidic sterol.