acnB Protein, E. coli

The acnB Protein plays a multifaceted role in the catabolism of short-chain fatty acids (SCFA) through both the tricarboxylic acid (TCA) pathway, specifically the acetyl degradation route, and the 2-methylcitrate cycle I, associated with propionate degradation. This enzyme exhibits catalytic versatility, facilitating the reversible isomerization of citrate to isocitrate via cis-aconitate, as well as the hydration of 2-methyl-cis-aconitate to generate (2R,3S)-2-methylisocitrate. Beyond its metabolic functions, the apo form of AcnB serves as a RNA-binding regulatory protein, particularly during oxidative stress. In this state, the inactive AcnB apo-enzyme lacking iron-sulfur clusters binds the acnB mRNA 3' untranslated regions, stabilizing acnB mRNA and augmenting AcnB synthesis. This intricate regulatory mechanism establishes a post-transcriptional positive autoregulatory switch. Additionally, AcnB influences the stability of the sodA transcript, revealing its broader impact on cellular processes beyond its primary metabolic functions.