= Neutrophil elastase
<Neutrophil elastase> is a <serine protease> stored in granules of <neutrophils>. Its ability to cleave <proteins> can alter structures outside or within the cell, depending on where the active <enzyme> is located. A particularly illuminating example connects <proteolysis> to organization of <chromatin>.<Neutrophil elastase and myeloperoxidase regulate the formation of neutrophil extracellular traps by Venizelos Papayannopoulos and others>[Abstract, granular localization and histone cleavage]{ref}
In a 2010 study, activation caused <neutrophil elastase> to reach the <cell nucleus>, where it partly degraded particular <histones>. Experiments with isolated nuclei and purified enzyme connected that cleavage to chromatin decondensation; <Western blot> measurements followed the protein changes. The study also found defective <neutrophil extracellular trap> formation in mice lacking the enzyme in its tested infection model.<Neutrophil elastase and myeloperoxidase regulate the formation of neutrophil extracellular traps by Venizelos Papayannopoulos and others>[Abstract and Fig. 1E–I, histone processing, purified enzyme and nuclear decondensation]{ref}
This separates several kinds of evidence. Observing a <protein> at a location is different from measuring its catalytic effects there. Combining localization, an <enzyme assay> and a loss-of-function comparison provides stronger mechanistic support than treating all three observations as equivalent.
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