A study of the transamination reaction by use of isotopic nitrogen.

The general nature of the biological transamination reaction (1) has been amply demonstrated in the past few years (2-7). It has been suggest’ed (8) that the coenzyme, via alternate interconversions into pyridoxal and pyridoxamine phosphates, functions as t’he shuttle of the amino groups in these reactions. If this mechanism is valid, it t’hen follows that enzymatic transaminations between the coenzyme and a-amino or cu-keto acids should be as wide-spread as between the amino acid pairs themselves. As an instance of this, we have studied the enzymatic transaminations between a-ketoglutarate and Nl5-labeled pyridoxamine in a pig heart homogenate. The validity of t’his approach for an investigation of the mechanism of the transamination reaction was first t’ested in experiment,s in which N15-labeled amino acids were the amino donors to cr-ketoglutarate.