AibA/AibB Induces an Intramolecular Decarboxylation in Isovalerate Biosynthesis by Myxococcus xanthus

Abstract

Isovaleryl coenzyme A (IV-CoA) is an important precursor for iso-fatty acids and lipids. It acts in the development of myxobacteria, which can produce this compound from acetyl-CoA through alternative IV-CoA biosynthesis (aib). A central reaction of aib is catalyzed by AibA/AibB, which acts as a cofactor-free decarboxylase despite belonging to the family of CoA-transferases. We developed an efficient expression system for AibA/AibB that allowed the determination of high-resolution crystal structures in complex with different ligands. Through mutational studies, we show that an active-site cysteine previously proposed to be involved in decarboxylation is not required for activity. Instead, AibA/AibB seems to induce an intramolecular decarboxylation by binding its substrate in a hydrophobic cavity and forcing it into a bent conformation. Our study opens opportunities for synthetic biology studies, since AibA/AibB may be suitable for the production of isobutene, a precursor of biofuels and chemicals.

Crystal structure of cis -aconitate decarboxylase reveals the impact of naturally occurring human mutations on itaconate synthesis

“…Unlike many other decarboxylases (33), human and mouse CAD did not require a cofactor for catalytic activity, which is consistent with the results by Dwiarti et al (34), who first described enzyme properties of purified aCAD. The CADs therefore establish a new class of the diverse but otherwise relatively rare cofactor-free decarboxylases (33, 35–41). In addition to IDS epimerase, prokaryotic 2-methylcitrate dehydratase also shares structural similarity with CAD.…”

The Alkylquinolone Repertoire of Pseudomonas aeruginosa is Linked to Structural Flexibility of the FabH‐like 2‐Heptyl‐3‐hydroxy‐4(1H)‐quinolone (PQS) Biosynthesis Enzyme PqsBC

“…Cloning and site‐directed mutagenesis : The pqsB (PA0997) and pqsC (PA0998) genes from P. aeruginosa PAO1 were amplified from chromosomal DNA by PCR (primers listed in Table S4). pqsB was cloned into pET26b (Merck Millipore), and pqsC was ligated into pET19m or p10$, both based on the pET19b vector (Merck Millipore). The resulting plasmid pET19m‐ pqsC produced PqsC with an N‐terminal His 6 tag followed by a recognition motif for TEV (tobacco etch virus) protease, whereas p10$‐ pqsC encoded PqsC with an N‐terminal His 6 ‐tagged T7 lysozyme removable by human rhinovirus 3C protease.…”

The isoprenoid alcohol pathway, a synthetic route for isoprenoid biosynthesis

“…3A). Subsequent dehydration (26), decarboxylation (27), and reduction results in the generation of prenol (Fig. 3A).…”

“…Although enzymes catalyzing the condensation steps, dehydration (26) and 3-methylglutaconyl-CoA decarboxylation (27) of this upper IPA pathway design have been established, identification of specific enzyme(s) for reducing 3-methylcrotonyl-CoA to prenol was required (Fig. 3A).…”