An alternative purification method for human serum paraoxonase 1 and its interactions with sulfonamides.

Paraoxonase 1 (PON1), a high-density lipoprotein (HDL)-associated esterase, is known to mediate antioxidant and antiatherogenic properties. Purification of PON1 has been challenging for a long time. Here, we report a novel purification technique for this enzyme, which allowed us to obtain human serum paraoxonase 1 (hPON1) using straightforward chromatographic methods, such as Diethylaminoethyl-Sephadex anion exchange chromatography and Sepharose 4B-4-phenylazo-2-naphthaleneamine hydrophobic interaction chromatography. We purified the enzyme 302-fold with a final specific activity of 4775 U/mg and a yield of 32\%. Furthermore, we examined the in vitro effects of some sulfonamide derivatives, such as sulfacetamide, homosulfanilamide (mafenide), sulfosalazine, furosemide, acetazolamide, and 1,3,4-thiadiazole-2-sulfonamide on the enzyme activity to better understand the inhibitory properties of the molecules. The six sulfonamides dose-dependently decreased the activity of hPON1 with inhibition constants in the millimolar-micromolar range. This study provides an efficient method, which may be useful for other enzymes such as those related to acetylcholinesterase. It also demonstrates the off-target activity of sulfonamides.