Deoxyribonuclease I (DNAse I) is an endonuclease that cleaves DNA phosphodiester bonds yielding 5_-phosphorylated and 3_-hydroxylated oligonucleotides. DNAse I targets single-stranded DNA, double-stranded DNA, and chromatin in a non-specific manner.As an important player in cellular waste management, DNAse I is normally secreted extracellularly to clear the system from circulating cell-free DNA, foreign DNA from food digestion or potential pathogens, and endogenous chromosomal DNA from apoptotic and necrotic cells. Abnormal DNAse I activity occurs in association with a variety of cancers and auto-immune illnesses that exhibit elevated levels of cell-free DNA. Furthermore, DNAse I has been therapeutically used in cystic fibrosis patients to degrade DNA and reduce sputum viscosity. DNAse I Activity Fluorometric Assay Kit allows for quantitative evaluation of DNAse I activity of purified enzymes and their inhibitors as well as comparative examination of DNAse I activity in biological samples. Enzyme activity is detected upon cleavage of a DNA Probe, which yields a fluorescent DNA product measured at Ex/Em = 651/681 nm. The limit of quantification (L.O.Q) is 178 fmoles of DNA probe cleaved per minute per ml.