resorufiinikineen

Resorufiinikineen is the Finnish term for the enzyme resorufin kinase, a member of the Nucleoside Monophosphate Kinase family that catalyzes the phosphorylation of the fluorescent dye resorufin to produce resorufin‑5′‑monophosphate. The enzyme uses ATP as the phosphate donor and operates optimally at physiological pH 7.4–8.0 at temperatures around 37 °C. Structural studies indicate that resorufiinikineen adopts a Rossmann-like fold with a conserved Lys‑X‑Gly‑X‑Gly motif essential for nucleotide binding. The catalytic mechanism involves a phosphoryl transfer from the γ‑phosphate of ATP to the 5′‑hydroxyl group of resorufin.

Resorufiinikineen is reported in several gram‑negative bacterial species, where it participates in the intracellular degradation of the redox‑active dye resorufin, a commonly used probe for monitoring cellular metabolism and oxidative stress. In Bacillus subtilis and Escherichia coli, the enzyme is encoded by the rufK gene, which is part of a regulon activated by high levels of exogenous resorufin. The enzyme shows low homology to human protein kinases, suggesting limited host cross‑reactivity and making it a potential target for selective antimicrobial agents that disrupt dye metabolism.

The phospho‑resorufin product is a stable fluorescing intermediate that can be employed as an internal standard in high‑performance liquid chromatography assays for quantifying resorufin accumulation. Researchers also use resorufiinikineen activity as a readout in studies of bacterial cell membrane integrity and response to environmental stressors. While the physiological role of resorufiinikineen in natural settings remains under investigation, its enzymatic activity offers valuable insights into bacterial redox biology and facilitates development of novel fluorescent assays.