Effects of chemical modification on enzyme activity and stability of bromoperoxidase from a thai seaweed

Abstract

Bromoperoxidase is the haloperoxidase enyme that catalyzes the peroxidatKe brominalion ol organic substrates to give an inlense color produet(si Phis tact offers a wide range of possibilities for bromoperoxidase in eommerieal applications especially in chemical synthesis and analytical diagnosis In this study, a non-heme bromoperoxidase from a fhai red seaweed, (.jrucilarhi chan-4ii. was purified and characterized by a DF.-52 column chromatograph and I'11.0 using Mono Q and Superose 12 columns. Bromoperoxidase from Ci thungii contains mo isoenymes, BPO and BPO2: both were shown to be non-heme enymcs by the absence of the Soret hand and were also shown to contain vanadiun as prosthetic group. In an attempt to increase stability and aethity oi' broinoperoxidase. chemical moditltahons ot the enyme b several reagents were studied. C'hemical modification of BPO t b 2.4.6,-trinitrobenene sut tonic acid and lodoaeetamide caused 2-and 5-fold increase in enynie actiity. and enhanced thermostahility in both acidic and alkaline conditions. Modification by Naeeryliniîdaole, diethylpyrocarb<inate, 5 5'-dithiobis (2-nitrobenzoic acid) and 1.2-cyciohexanedione did not cause any change in activity and stability of BPO I. None of these modifying agents caused an increase in cither activity and stability of BPO2. From amino acid analysis of iodoace t amide-modi tied BPOi. 1-4 ot'total 42 lysyl residues and 6 of total 30 histidyl residues were modified, suggesting the involvement ol modified lysyl and histidyl residues in the enhancement of cn>me activity and stability.