Aspartoacylase deficiency does not affect N-acetylaspartylglutamate level or glutamate carboxypeptidase II activity in the knockout mouse brain

Aspartoacylase (ASPA)-deficient patients [Canavan disease (CD)] reportedly have increased urinary excretion of N-acetylaspartylglutamate (NAAG), a neuropeptide abundant in the brain. Whether elevated excretion of urinary NAAG is due to ASPA deficiency, resulting in an abnormal level of brain NAAG, is examined using ASPA-deficient mouse brain. The level of NAAG in the knockout mouse brain was similar to that in the wild type. The NAAG hydrolyzing enzyme, glutamate carboxypeptidase II (GCP II), activity was normal in the knockout mouse brain. These data suggest that ASPA deficiency does not affect the NAAG or GCP II level in the knockout mouse brain, if documented also in patients with CD.