Purification and Characterization of Cathepsin B Inhibitors from a marine Pseudomonas sp. strain PB01

Abstract

A novel cathepsin B inhibitor-producing microorganism was identified based on its 16S rRNA sequence as Pseudomonas sp. strain PB01 (accession no. EU126129). Before isolating inhibitors, enzyme inhibitors production was investigated under various culture conditions, including temperature, initial medium pH, and shaking speed. Additionally kinetic study revealed that the inhibitor production paralleled with cell growth. From the culture broth, two cathepsin B inhibitors were isolated, which structural characterizations were elucidated as phthalates. Both of them inhibited cathepsin B dose dependently with IC50 of 0.42 and 0.38 mM, respectively. Kinetic analyses showed that dibutyl phthalate and di-(2-ethylhexyl) phthalate acted in noncompetitive manners, which were agreeable with their characteristics. Furthermore, both of them not only caused inactivation of the pericellular but also intracellular cathepsin B of murine melanoma cell with no acute cytotoxicity.