Synthesis of Shikimic Acid-C¹⁴in Pinus Resinosa, AIt. From Some C¹⁴-Labelled Compounds

The shikimic acid (SA) content of Pinus resinosa twigs was found to range from 0.2–2.12 g fresh weight, depending on the season of the year. Of the radioactive compounds administered to cut shoots, pyruvic acid gave SA of the highest specific activity. Sugars were next most effective, with glucose and ribose being better than sucrose and fructose. Carbon from several organic acids was not readily incorporated into SA. Pyruvate-3-C 14 gave SA of higher specific activity than did pyruvate-1-C 14 or -2-C 14 . When pyruvate-1-C 14 was used, 40% of the activity in shikimic acid was in the carboxyl carbon, whereas with pyruvate-2-C 14 or -3-C 14 only 3–10% of it was in the carboxyl carbon. The results with pyruvate can best be explained in terms of the "dicarboxylate shuttle". When either erythrose or 5-dehydroshikimic acid was administered together with pyruvate-C 14 , a decrease in specific activity of SA was observed. These results are consistent with the view that in Pinus, SA is synthesized from phosphoenolpyruvate and erythrose-4-phosphate through dehydroshikimic acid.