Biochimica et biophysica acta最新文献

• 1.

  1. A new enzyme which catalyses the reversible condensation of pyruvate and glyoxylate to form γ-hydroxy-α-ketoglutarate was purified in excess of 120-fold from rat-liver acetone powder.

• 2.

  2. The enzyme was specific for glyoxylate and pyruvate. Condensation could not be demonstrated between other aldehydic acids and keto acids which were tested, distinguishing this enzyme from the formaldehyde and pyruvate condensing enzyme (2-oxo-4-hydroxybutyrate formaldehyde-lyase, EC 4.1.2.1) and the cleavage enzyme of γ-hydroxyglutamate (4-hydroxyglutamate glyoxylate-lyase). The apparent K_m values (at optimal pH, 7.5) for pyruvate, glyoxylate and γ-hydroxy-α-ketoglutarate were 10 mM, 0.43 nM and 1.33 mM, respectively. The equilibrium facors the biosynthesis of γ-hydroxy-α-ketoglutarate.

• 3.

  3. The product of the enzymic condensing reaction was isolated as the Ca salt and identified as γ-hydroxy-α-ketoglutaric acid from its chemical properties.

• 4.

  4. On the basis of the experimental findings, the possible metabolic pathways of pyruvate, glyoxylate and γ-hydroxyglutamate (the main oxidation product of L-hydroxyproline) and the regulating role of glyoxylate for the tricarboxylic acid cycle were discussed.

Ethanol-fractionated human transferrin (transferrin CC) separates into two fractions when subjected to chromatography on anion-exchange cellulose (CM-cellulose). The two fractions show similarities in their immunological, biological and physical properties. Some differences in their carbohydrate composition are demonstrated.

The same separation pattern of transferrin is found if whole serum from individual donors is subjected to the same chromatographic procedure.

• 1.

  1. Resulta of a study of the degradation of kynurenic acid by an Aerococcus are in agreement with a reaction sequence proposed for Pseudomonas by other workers. This sequence includes Compounds I and II below.

• 2.

  2. Partial inhibition of oxidation of kynurenic acid by cell suspensions caused an accumulation of pyruvate with arsenite as inhibitor; α-ketoglutarate and aspartate accumulated when semicarbazide was used.

• 3.

  3. Crystals of Compound II, having properties expected for 5-β(carboxyethyl)-4,6-dihydroxypicolinic acid were isolated from cultures of the Aerococcus oxidizing kynurenic acid.

• 4.

  4. The properties are described of a solution of purified Compound I, also isolated from culture fluids. These properties are those expected for 5-(γ-carboxy, γ-oxopropenyl)-4,6-dihydroxypicolinic acid.

• 5.

  5. Dialysed cell-free extracts converted 7,8-dihydroxykynurenic acid to Compound I; the latter was degraded when reduced triphosphopyridine nucleotide was added to the extract.

• 6.

  6. Compound II was degraded by cell-free extracts; pyruvate, α-ketoglutarate, aspartate and glutamate were identified as reaction products; and when extracts were inhibited by semicarbazide the first of these compounds to appear were aspartate and α-ketoglutarate.

• 7.

  7. Evidence is presented that xanthurenic acid is not an intermediate in the conversion of kynurenic to 7,8-dihydroxykynurenic acid.

• 8.

  8. The Aerococcus and a Rhodotorula both attacked picolinic acid, and 6-hydroxypicolinic acid was isolated from arsenite-inhibited cultures.

• 9.

  9. Cell-free extracts of Rhodotorula converted picolinic to 6-hydroxypicolinic acid. The reaction can occur anaerobically in the presence of methylene blue and resembles the conversion of nicotinic acid to 6-hydroxynicotinic acid described by other workers for Pseudomonas.

Rabbit γ-globulin was resolved into two fractions by chromatography of normal or immune serum on a DEAE-Sephadex column at pH 8. Different distribution of antibodies from the different antisera among the two γ-globulin fractions was observed.

Upon hydrolysis by papain followed by separation of the fragments formed, both γ-globulin fractions yielded the same amount of fragment III; one of them gave in addition a double amount of fragment II and the other a double amount of fragment I. This provides additional evidence that γ-globulin molecules are composed of two identical pieces (fragments I or II) together with fragment III.