Examining the Metabolic Role of the Pseudomonas aeruginosa MDO Operon

Abstract

Mammalian cysteine dioxygenase (CDO) is a mononuclear iron enzyme that catalyzes the oxidation of L‐cysteine to L‐cysteine sulfinic acid. It contains an amino acid‐derived cofactor formed between residues Cys93‐Tyr157. Putative CDO enzymes have been identified in several bacteria; however, all known bacterial CDO enzyme homologs lack the Cys‐Tyr amino acid‐derived cofactor. 1Although the MDO enzyme has been proposed to convert 3‐mercaptopropionate (3‐MPA) to 3‐sulfinopropionate (3‐SPA), the physiological function of either 3‐MPA or 3‐SPA remains unclear. 2,3In numerous bacteria, the MDO gene is on the same operon as an annotated sulfurtransferase, and the operon is expressed during bacterial sulfur limitation. The sulfurtransferase has amino acid sequence similarity to mercaptopyruvate sulfurtransferase enzymes.Different thiol‐containing substrates were evaluated to support a defined metabolic pathway involving both MDO and the sulfurtransferase. MDO gave similar catalytic parameters with both 3‐MPA and mercaptopyruvate, suggesting that both are viable substrates for the enzyme. However, the specificity of MDO for mercaptopyruvate correlates with the classification of the coexpressed sulfurtransferase. Therefore, MDO and the sulfurtransferase enzymes may be metabolically linked, and optimal catalytic function could involve protein‐protein interactions between the two enzymes. Potential protein‐protein interactions between MDO and the sulfurtransferase were identified by surface plasmon resonance, and hydrogen‐deuterium exchange was performed to further identify where the interaction sites of MDO and the sulfurtransferase are located. Coupling of MDO with the sulfurtransferase was also investigated to understand the functional role of the enzymes in bacteria. The proposed overall mechanism for both enzymes would result in sulfite release that could be utilized in the sulfur assimilation pathway. Based on these findings, the MDO/sulfurtransferase system represents an additional pathway for bacteria to adapt to sulfur limiting conditions that had not been previously identified.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.