Research on Some Freshwater Fish Catalase Activity - As a Potential Biomarker for Environmental Pollution

In the last decade studies show that water pollution is a very serious problem, especially since the degree of water pollution plays a key role in the growth and fish multiplication. As a biomarker of environmental pollution, antioxidant enzymes such as catalase (CAT; EC 1.11.1.6) play an essential role in preventing the harmful effects of heavy metals in the tissues of fish. These researches were carried out to investigate the effect of various environment conditions and some pollutant agents on oxidative stress in some aquatic organisms. The enzymatic assay of CAT (in fish organs, e.g., liver, kidney, gill, intestine and brain, as well as in mixture of these organs) was carried out according to standard enzyme assay protocol. The results showed decrease of CAT activity: the enzymatic activity was 35.89 ± 1.02 µmol H2O2/min/mg protein to pH 7 and 6.59 ± 0.47 µmol H2O2/min/mg protein to pH 12. More, the enzymatic activity was 38.1 ± 0.3 µmol H2O2/min/mg protein to pH 3. Also, the catalase activity increased with 23 enzymatic units to a less dissolved oxygen concentration (6.2877 mg/L). Furthermore, this study indicated that heavy metals, such as Cr, Cu and Zn can inhibit biochemical reactions in various organs of fish. During exposure duration of the fish to a mixture of metal ions the catalase activity decreases from 35.89 ± 1.02 µmol H2O2/min/mg protein to 23.51 ± 2.85 µmol H2O2/min/mg protein. On the other hand, as a result of the response of the enzyme system, the catalase activity increases to 36.25 ± 3.22 µmol H2O2/min/mg protein.