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TRANSAMINATION OF AMINO ACIDS IN HOMOGENATES OF RAT BRAIN
Author(s) -
Benuck M.,
Stern F.,
Lajtha A.
Publication year - 1971
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1971.tb00017.x
Subject(s) - transamination , amino acid , biochemistry , citrate synthase , alanine , phenylalanine , glutamate receptor , methionine , metabolism , biology , leucine , tyrosine , chemistry , enzyme , receptor
— The aminotransferase activity of homogenates of brains from adult and neonatal rats has been investigated. Aminotransferase activity was demonstrated wtih 15 of 22 amino acids incubated with seven keto acids. The basic amino acids exhibited little or no activity.1 The greatest activity was obtained when glutamate or aspartate was incubated with α‐ketoglutarate or oxaloacetate. Significant activity was also observed when the neutral aliphatic and aromatic amino acids were incubated with these two keto acids. 2 Activity with pyruvate was obtained principally upon incubation with glutamate and alanine. Most of the other amino acids that underwent transamination with α‐ketoglutarate also did so with pyruvate, although at a lower rate. 3 When phenylpyruvate was added to the medium, glutamate, phenylalanine and tyrosine transaminated most actively. 4 Incubations with 11 amino acids and glyoxylic acid demonstrated aminotransferase activity, with glutamate and ornithine being the most active substrates. 5 α‐Ketoisocaproate and α‐ketoisovalerate accepted amino groups primarily from the branched‐chain amino acids. Except for glutamate, activity with other amino acids was low or not detectable. 6 A comparison of aminotransferase activity in the newborn brain with that in the adult brain showed that the greatest change in activity occurred for glutamate with pyruvate or for alanine with α‐ketoglutarate, these activities increasing about 10‐fold from birth to adulthood; during this time activities with most other amino acids increased two‐ to threefold. Amino transfers from the branched‐chain amino acids showed no increase with maturation, and some reactions, such as that with methionine and a number of keto acids, decreased from birth to adulthood. 7 Our results correspond in general to previous studies of aminotransferase activity in brain and in liver. However, our study also indicates a possible second aminotransferase acting on the branched‐chain amino acids, the presence of aminotransferase activity for methionine and asparagine, and relatively high aminotransferase activity for glutamine or ornithine when incubated with glyoxylic acid rather than other keto acids. Moreover, phenylpyruvate and glyoxylate are active in amino transfers and may serve as substrates for a number of aminotransferases.