- Monday, October 23, 2006
- Photoilluminated riboflavin/riboflavin-Cu(II) inactivates trypsin: Cu(II) tilts the balance.
- Published at:Indian J Biochem Biophys
Indian J Biochem Biophys. 2006 Oct;43(5):312-8.
Photoilluminated riboflavin/riboflavin-Cu(II) inactivates trypsin: Cu(II) tilts the balance.
Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202 002 (U.P.), India.
Riboflavin (RF) upon irradiation with fluorescent light generates reactive oxygen species like superoxide anion, singlet and triplet oxygen, flavin radicals and substantial amounts of hydrogen peroxide (H2O2). H2O2 can freely penetrate cell membrane and react with a transition metal ion like Cu(ll), generating hydroxyl radical via the modified metal-catalyzed Haber-Weiss reaction. Earlier, it was reported that trypsin-chymotrypsin mixture served as an indirect antioxidant and decreased free radical generation. Thus, in the present study, we used photoilluminated RF as a source of ROS to investigate the effect of free radicals on the activity of trypsin. We also compared the damaging effect of photoilluminated RF and RF-Cu(ll) system using trypsin as a target molecule. RF caused fragmentation of trypsin and the effect was further enhanced, when Cu(II) was added to the reaction. Results obtained with various ROS scavengers suggested that superoxide radical, singlet and triplet oxygen were predominantly responsible for trypsin damage caused by photoilluminated RF. On the other hand, when Cu(ll) was added to the reaction, hydroxyl radical was mainly responsible for trypsin damage. A mechanism of generation of various ROS in the reaction is also proposed. Trypsin did not show any antioxidant effect with RF alone or with RF-Cu(II) combination.