ISOLATION AND CHARACTERIZATION OF A PEROXIDASE FROM THE AIRWAY

Sheep airway mucus can potently scavenge hydrogen peroxide, an importa nt mediator of airway inflammation, Here, the scavenging activity was identified as a peroxidase produced by goblet cells of the airway epit helium and secreted into the ah-way lumen, Ovine airway peroxidase act ivity was purified similar to 100-fold from airway lavage fluid in two steps, using cation exchange and lectin affinity chromatography, yiel ding an apparently homogeneous 82-kD glycoprotein, Ovine airway peroxi dase represented about 1% of the total protein in ah-way mucus and thu s was an abundant enzyme in airway secretions. The absorbance spectrum of the purified peroxidase showed a major peak at 412 nm indicative o f a hemoprotein. The ratio of A(412)/A(280) of the purified enzyme was 0.86, The absorption spectrum of ovine airway peroxidase, its ability to oxidize halides, its sensitivity to inhibitors and its apparent mo lecular mass on sodium dodecyl sulfate gels showed that airway peroxid ase was similar to lactoperoxidase but distinguished from myeloperoxid ase, eosinophil peroxidase as well as from glutathione peroxidases, Ba sed on these observations, ovine airway peroxidase is a newly isolated and abundant enzyme of airway mucus which may function to control rea ctive oxygen species in the ah-way and to prevent infection by catalyz ing the formation of biocidal compounds.