The Induction of Proteolysis in Purulent Sputum by Iodides*

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Abstract
Iodides induce proteolysis in purulent sputum from patients with cystic fibrosis and other forms of respiratory disease. Proteolysis was enzymatic and depended upon the presence of natural leukocytic proteases or an added protease such as trypsin. Maximum proteolysis occurred in the presence of lM NaI, but proteolysis was also enhanced with 0.05 mM NaI over a more prolonged time interval. Naturally occurring iodinated thyroidal compounds were much more effective for inducing proteolysis than the inorganic iodides, and higher rates of proteolysis resulted from lower concentrations (5 [mu]M). There is a stoichiometric relationship between iodinated tyrosine and sputum-protein concentrations. The L-isomers of these thyroidal compounds promoted a higher rate of proteolysis than the D-isomers, when intact cells were present in the sputum preparation. Whether thyroxine and its precursors affect proteolysis in-vivo in cellular metabolism is not known. The possible clinical use of iodinated tyrosine compounds for thinning viscid purulent respiratory secretions is suggested.