Ustilago maydis produces itaconic acid via the unusual intermediate trans‐aconitate

Abstract

SummaryItaconic acid is an important biomass‐derived chemical building block but has also recently been identified as a metabolite produced in mammals, which has antimicrobial activity. The biosynthetic pathway of itaconic acid has been elucidated in the ascomycetous fungus A spergillus terreus and in human macrophages. In both organisms itaconic acid is generated by decarboxylation of the tricarboxylic acid (TCA) cycle intermediate cis‐aconitate. Here, we show that the basidiomycetous fungus U stilago maydis uses an alternative pathway and produces itaconic acid via trans‐aconitate, the thermodynamically favoured isomer of cis‐aconitate. We have identified a gene cluster that contains all genes involved in itaconic acid formation. Trans‐aconitate is generated from cis‐aconitate by a cytosolic aconitate‐Δ‐isomerase (Adi1) that belongs to the PrpF family of proteins involved in bacterial propionate degradation. Decarboxylation of trans‐aconitate is catalyzed by a novel enzyme, trans‐aconitate decarboxylase (Tad1). Tad1 displays significant sequence similarity with bacterial 3‐carboxy‐cis,cis‐muconate lactonizing enzymes (CMLE). This suggests that U . maydis has evolved an alternative biosynthetic pathway for itaconate production using the toxic intermediate trans‐aconitate. Overexpression of a pathway‐specific transcription factor (Ria1) or a mitochondrial tricarboxylic acid transporter (Mtt1) resulted in a twofold increase in itaconate yield. Therefore, our findings offer new strategies for biotechnological production of this valuable biomass‐derived chemical.

Activating Intrinsic Carbohydrate-Active Enzymes of the Smut Fungus Ustilago maydis for the Degradation of Plant Cell Wall Components

“…However, further development by the above-described strategies could still eventually yield a competitive system. In addition, the biosynthesis pathways for itaconic acid as well as for the potentially interesting glycolipids have been described in detail, and initial attempts of metabolic engineering have already demonstrated their potential to increase productivity (27,86,87).…”

“…Members of the Ustilaginaceae smut fungi are promising natural producers of organic acids (21,26,27). Within this group of biotrophic plant pathogens, Ustilago maydis is of increasing interest, not least due to its long history of intensive investigation as a paradigm of plant-pathogen interaction (28).…”

Emerging biotechnologies for production of itaconic acid and its applications as a platform chemical

“…Huang et al [33] overexpressed cadA and mfsA (major facilitator superfamily transporter) genes in A. terreus and obtained enhanced IA production level by 9.4 and 5.1% in shake flasks, respectively, in comparison to wild type. Geiser et al [23] reported that overexpression of a pathway-specific transcription factor (Ria1) or a mitochondrial tricarboxylic acid transporter (Mtt1) in U. maydis resulted in a 2-fold increase in IA yield.…”

“…Recently, Gieser et al [23] showed that the fungus Ustilago maydis, a phytopathogenic basidiomycete, uses an alternative pathway and produces IA via trans-aconitate, the thermodynamically favored isomer of cis-aconitate (Fig. 2).…”

“…Trans-Aconitate is decarboxylated by Tad1 giving rise to itaconate. Reproduced from Geiser et al[23]. Published by John Wiley & Sons proteins involved in bacterial propionate degradation.…”