nahDAHV

NahDAHV is a designation used in some bacterial genome annotations for a putative four-gene operon comprising nahD, nahA, nahH, and nahV. The cluster has been reported in several environmental bacterial genomes associated with hydrocarbon degradation, but its exact function remains uncertain. In many annotations, nahDAHV is treated as a single transcriptional unit with co-regulated expression, though the precise boundaries and gene order can vary between species.

Genomic organization and predicted products: The operon is typically described as containing four adjacent open reading frames. Predicted products, based on sequence similarity to known families, include enzymes of oxidoreductase or dehydrogenase-like function for nahD and nahA, and regulatory or sensor-associated roles for nahH and nahV. The locus is often found near other genes involved in catabolic pathways, transport, or ring-cleavage enzymes, supporting a potential involvement in aromatic compound metabolism.

Proposed roles and evidence: There is no experimentally demonstrated function for nahDAHV to date. Functional inferences are tentative and rely on homology-based predictions. The cluster is often hypothesized to participate in the initial steps of aromatic compound oxidation, redox balancing during degradation, or the regulation of nearby catabolic genes, but these roles have not been confirmed in vitro or in vivo.

Distribution and evolution: NahDAHV-like loci have been identified in a limited set of bacterial lineages, particularly within environmental isolates from hydrocarbon-contaminated sites. The variable presence and diverse genomic contexts suggest a history of horizontal gene transfer and modular rearrangement.

See also: Naphthalene degradation operons; Aromatic compound catabolism; Gene clusters.