Bacterial and mitochondrial enzymes containing sulfhydryl groups

Bacterial and mitochondrial enzymes containing sulfhydryl groups are a diverse set of proteins involved in essential metabolic pathways, such as the citric acid cycle and the synthesis of DNA, RNA, and proteins (StatPearls, 2023). These enzymes are characterized by the presence of reactive thiol (-SH) groups that are necessary for their catalytic activity or structural integrity. They serve as the primary site of action for nitrofurantoin and other nitrofuran antibiotics, which are activated within bacterial cells (PubChem, 2024). Bacterial nitroreductases reduce these drugs into highly reactive, short-lived electrophilic intermediates that form covalent bonds with the sulfhydryl groups of the target enzymes, leading to irreversible inhibition (DrugBank, 2024). This multi-faceted attack on various metabolic enzymes explains the broad-spectrum bactericidal activity of nitrofurans and the low frequency of developed resistance. While the activation is primarily specific to bacterial enzymes, the similarity between bacterial and human mitochondrial enzymes can lead to off-target toxicity in host tissues. Consequently, these enzymes are critical for understanding both the therapeutic efficacy and the safety profile of nitrofuran therapy.

Other names

Sulfhydryl-containing enzymesThiol-dependent enzymesBacterial metabolic enzymesSulfhydryl-dependent bacterial enzymes

Nitrofurans are reduced by bacterial flavoproteins (nitroreductases) to highly reactive electrophilic intermediates. These intermediates non-specifically attack and covalently bind to nucleophilic sites on bacterial and mitochondrial enzymes, particularly those containing essential sulfhydryl (-SH) groups. This leads to the inactivation of multiple metabolic pathways, including the citric acid cycle and the synthesis of DNA, RNA, and proteins (StatPearls, 2023; DrugBank, 2024).