δ‐Aminolevulinic acid biosynthesis in Ustilago maydis

A biosynthetic precursor of tetrapyrroles, δ‐aminolevulinic acid (ALA), can be formed via two pathways: enzymatic condensation of glycine and succinyl‐CoA by ALA synthase in animal mitochondria and some fungi, and the C 5 pathway converting glutamate to ALA in plants, algae, archaea, and most bacteria. The two pathways are distinguishable using specifically radiolabeled compounds. The C 1 of glutamate is lost during conversion to succinate in the TCA cycle, and the C 2 of glycine is lost during conversion to acetyl‐CoA on the way to glutamate. Desalted high‐speed supernatants of Ustilago maydis sporidia extracts were assayed using specifically radiolabeled substrates. A significant amount of radiolabel was incorporated into ALA from 2‐[ 14 C]glycine. No radiolabel was incorporated into ALA from 1‐[ 14 C]glutamate. These results indicate that the basidiomycete yeast, Ustilago maydis , has active ALA synthase. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)