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Immediate report of Victoria University of Wellington Antarctic Expedition 1988-89: VUWAE 33

GLUTATHIONE S-TRANSFERASES FROM ANTARCTIC FISH. A comparative study of enzymes with those from rat, a temperate fish and an Insect

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GLUTATHIONE S-TRANSFERASES FROM ANTARCTIC FISH. A comparative study of enzymes with those from rat, a temperate fish and an Insect.

Abstract

Glutathione S-transferase activity was found in liver homogenates from Antarctic fish species Dissostichus mawsoni and Pagothenia borchgrevinki. Activities measured with 1-chloro-2, 4-dinitrobenzene were 11.2 μmol min−1 mg−1 and 16.7 μmol min−1 mg−1 respectively. Little or no activity was detected with p-nitrobenzyl chloride or 3,4-dichloro-1-nitrobenzene. Glutathione was found in the livers of Antarctic fish in millimolar quantities.

The partial purification of glutathione S-transferases from D. mawsoni is described.

The effects of temperature and pH on the spontaneous and enzyme catalysed reaction are described. The spontaneous reaction rate being characterized by the activation parameters (A=26.33±0.7, ΔH# = 50.71±1.67 KJ mol−1) and the sulphdryl proton ionization parameters (ΔH=31.4±2.5 KJ mol1−1, ΔS = 72±8 J mol−1 K−1).

The effects of pH on the glutathione S-transferase from G. mellonella are examined. The reduction in catalytic action at high pH being due to ionizations associated with flutothione binding (pKa 8.6±0.2, 9.2±0.2).

The effects of temperature are discussed in both thermodynamic terms and in the ability to enhance the spontaneous reaction. Isoenzymes from rat, G. mellonella and D. mawsoni are characterized. Rate enhancement factors were within a ten fold range, suggesting antarctic fish have an effective detoxication system.

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