The metabolism of γ-hydroxyglutamate in rat liver II. A transaminase concerned in γ-hydroxyglutamate metabolism

Abstract

• 1.

  1. An enzyme which catalyses the transamination between γ-hydroxyglutamate and α-ketoglutarate was extracted from rat-liver acetone powder and purified in excess of 15-fold. Fractionation of the enzyme from a separate aspartate transaminase (L-aspartate: 2-oxoglutarate aminotransferase, EC 2.6.1.1) remained incomplete.

• 2.

  2. [2-¹⁴C]Pyruvate was incorporated into γ-hydroxy-α-ketoglutarate and γ-hydroxyglutamate in the presence of glyoxylate in rat-liver homogenate. Specific activity values of these three compounds indicated the occurence of the following pathway: Pyruvate + glyoxylate ⇌ γ-hydroxy-α-ketoglutarate ⇌ γ-hydroxyglutamate.

• 3.

  3. A further possible pathway of γ-hydroxy-α-ketoglutarate metabolism leading to malate and of γ-hydroxyglutamate to its decarboxylation product or to L-hydroxyproline were inferred and discussed.