Identification and characterization of capsaicin-hydrolyzing enzymes purified from rat liver microsomes

To elucidate the metabolic pathway of capsaicin (CAP), CAP-hydrolyzing enzymes, involved in the initial step of hydrolysis, were purified from rat liver microsomes and were characterized. CAP-hydrolyzing enzymes, whose activity was assayed by HPLC, were found to be located in the lumen of endoplasmic reticulum (ER). The enzymes were extracted from microsomes with Triton X-100 and purified by DEAE-cellulose, Sephadex G-200 (superfine), and isoelectrofocusing (IEF) chromatography. The enzymes were eluted from a gel filtration column as peaks with relative molecular mass of 60,000 and 180,000; IEF using Rotofor Cell showed that pIs of these enzymes are around 5.6 and 6.1, respectively. Total CAP-hydrolyzing activity of enzyme pI 5.6 was much greater than that of enzyme pI 6.1. With several lines of criteria, these fully characterized enzymes were identified as previously known hydrolase pI 5.6 and hydrolase pI 6.1.