O. Yu. Vasylkiv, V. I. Lushchak
Vassyl Stephanyk Precarpathian National University, Ivano-Frankivsk, Ukraine;
Lactate dehydrogenase (LDH) from the liver and white muscles of the gold fish Carassius auratus was partially purified by differential precipitation with ammonium sulfate. The enzyme from the liver had relatively low Vmax – 1.85 ± 0.31?U/mg protein, the muscle enzyme – 3.74 ± 0.27 U/mg protein. LDH from the liver was less sensitive to substrate inhibition (I50 – 9.92 ± 1.09 mM) compared to white muscles isozyme (I50 – 5.87 ±?1.39?mM). The studied isozymes had pH-dependencies with pH optima at 7.0–8.0 and 7.25–8.75 for LDH from the white muscle and liver, respectively. In this work the inactivation of partially purified LDH in the system free radicals oxidations Fe2+/H2О2 has been conducted. During incubation for 5 min of both isozymes with H2О2 (10–50 mM) and FeSО4 (20–500 µM), approximately 50% of their initial activities were lost. The level of enzyme inactivation increased with the increase of iron ion and hydrogen peroxide concentrations. During incubation in the presence of 20 µM FeSО4 and 10 mM H2О2 for 60 min white muscles isozyme lost 44% while liver isozyme – 26%, independent of buffer which was used.
Key words: lactate dehydrogenase, Carassius auratus, inactivation.
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© The Ukrainian Biochemical Journal