The Metabolism of L-Pyroglutamic Acid in Fibroblasts from a Patient with Pyroglutamic Aciduria: The Demonstration of an L-Pyroglutamate Hydrolase System

Abstract

Intact fibroblasts cultured from skin biopsies from normal humans and from a patient with pyroglutamic aciduria were shown to metabolize L-pyroglutamate to CO₂ at a rate of about 7 mmol/min per g of fibroblast. An enzyme system hydrolyzing pyroglutamic acid to glutamic acid and requiring ATP, Mg⁺⁺, and K⁺, was found in the particle-free supernatant of fibroblasts. Its activity under optimal conditions was about 15 nmol/min per g of fibroblast protein. The apparent K_m for pyroglutamic acid was about 8 nmol/1 and for ATP about 25 nmol/l. The activity and the properties of the pyroglutamate hydrolase system were equal in fibroblasts from normal controls and the patient. The results are discussed in relation to the possible biochemical defect in pyroglutamic aciduria.

Key Words:

• ATP
• fibroblast culture
• glutamic acid
• inborn error
• pyroglutamic aciduria
• L-pyroglutamate hydrolase
• proline