Effects of calcium ions and quinolinic acid on rat kidney mitochondrial kynurenine aminotransferase |
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Authors: | M Mason |
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Institution: | Department of Biological Chemistry, The University of Michigan, Ann Arbor, Michigan 48104 USA |
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Abstract: | At pH 6.4, rat kidney mitochondrial kynurenine aminotransferase activity is enhanced several-fold by the addition of CaCl2, apparently because Ca++ facilitates the translocation of α-ketoglutarate, one of the substrates, across the mitochondrial inner membrane. Chloride salts or Mg++, Mn++, Na+, K+, and NH4+ did not have this effect. At pH 6.8, the enzyme activity was near maximal even without added Ca++ but was strongly depressed by either of two calcium chelating agents, quinolinic acid (Q.A.) and ethyleneglycol-bis(β-aminoethyl ether)N,N′-tetraacetic acid (EGTA). These observations support the view that Ca++ is involved in regulating kidney mitochondrial translocation of α-ketoglutarate and that the reported interference of polycarboxylate anion translocation by Q.A. depends on the ability of that agent to chelate Ca++. |
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Keywords: | Q A Quinolinic acid EGTA ethyleneglycol-bis-(β-aminoethyl ether)N N′-tetraacetic acid |
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