[Comparative characteristic of lactate dehydrogenase properties from the white muscles and liver of goldfish (Carassius auratus L.)].
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+/H2O2 has been conducted. During incubation for 5 min of both isozymes with H2O2 (10-50 mM) and FeSO4 (20-500 microM), 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 microM FeSO4 and 10 mM H2O2 for 60 min white muscles isozyme lost 44% while liver isozyme--26%, independent of buffer which was used.
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D000818:Animals; D005296:Ferrous Compounds / Q000494:pharmacology; D006054:Goldfish; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010084:Oxidation-Reduction; D013379:Substrate Specificity
D005296:Ferrous Compounds; C020748:ferrous sulfate; D006861:Hydrogen Peroxide; D007770:L-Lactate Dehydrogenase