Biosynthesis of hydrocarbons by algae: Decarboxylation of stearic acid to N‐heptadecane in Anacystis nidulans determined by 13 C‐ and 2 H‐labeling and 13 C nuclear magnetic resonance

The distribution of isotopic labels in n ‐heptadecane enriched from [1,2‐ 13 C] and [2‐ 13 C, 2‐ 2 H 3 ) acetates by Anacystis nidulans has been determined by 13 C nuclear magnetic resonance ( 13 C NMR). Labeling with [1,2‐ 13 C] acetate is consistent with assembly from 13 C− 13 C units derived from an acetate “starter” group and 8 malonate units, as in fatty acid biosynthesis, followed by production of a methyl group through bond cleavage of the terminal 13 C− 13 C unit. A comparison of the hydrocarbon with palmitic acid (the only fatty acid produced in sufficient amount for NMR analysis) enriched from [2‐ 13 C,2‐ 2 H 3 ]acetate by the same culture shows that they have retained the same fraction of 2 H at corresponding sites, and have therefore undergone identical biosynthetic and hydrogen‐deuterium exchange processes, as would be expected if n ‐heptadecane originates from de novo‐synthesized stearic acid.