N-terminal asparagine amidohydrolase (NTAN1) is an essential component of a protein degradation signal, which is a destabilizing N-terminal residue of a protein, in the N-end rule. The enzymatic deamidation of N-terminal L-Asn by NTAN1 is a feature of the ubiquitin-dependent N-end rule pathway of protein degradation, which relates the in vivo half-life of a protein to the identity of its N-terminal residue. NTAN1 deamidates N-terminal asparagine to aspartate, which is conjugated to arginine by ATE1. An N-terminal arginine-bearing substrate protein is recognized, ubiquitylated by UBR1/E3alpha, and subsequently degraded by 26S proteasomes. The approximately 17-kilobase pair Ntan1 gene is located in the proximal region of mouse chromosome 16 and contains 10 exons ranging from 54 to 177 base pairs in length. Inactivation of the NTAN1 gene encoding the asparagine-specific N-terminal amidase in mice results in impaired spatial memory.