Delta-aminolevulinic acid biosynthesis in Ustilago maydis.

A biosynthetic precursor of tetrapyrroles, delta-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 C5 pathway converting glutamate to ALA in plants, algae, archaea, and most bacteria. The two pathways are distinguishable using specifically radiolabeled compounds. The C1 of glutamate is lost during conversion to succinate in the TCA cycle, and the C2 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-[14C]glycine. No radiolabel was incorporated into ALA from 1-[14C]glutamate. These results indicate that the basidiomycete yeast, Ustilago maydis, has active ALA synthase.