Enzymic synthesis of L‐glutamic acid‐¹⁵N and 4‐aminobutyric acid‐¹⁵N and the preparation of L‐pyroglutamic acio‐¹⁵N

The production of L‐glutamic acid‐ 15 N in good yield by direct enzymic synthesis from 2‐oxoglutaric acid, ammonium chloride‐ 15 N (95 atom % 15 N) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) is described. The NADPH is continuously regenerated by coupling the first reaction to the oxidation of glucose‐6‐phosphate, which serves to drive the synthesis of L‐glutamic acid to completion. 4‐Aminobutyric acid‐ 15 N is produced by incubation of L‐glutamic acid‐ 15 N with glutamic acid decarboxylase. CO 2 is lost from the reaction mixture and the conversion of glutamic acid to 4‐aminobutyric acid proceeds to completion. L‐Pyroglutamic acid‐ 15 N is produced by heating aqueous solutions of L‐glutamic acid‐ 15 N at 135° for 3 hours.