Protein N-terminal asparagine amidohydrolase (NTAN1) acts on the side-chain deamidation of N-terminal asparagine residues to aspartate. It is required for the ubiquitin-dependent turnover of intracellular proteins that initiate with Met-Asn. These proteins are acetylated on the retained initiator methionine and can subsequently be modified by the removal of N-acetyl methionine by acylaminoacid hydrolase (AAH). Conversion of the resulting N-terminal asparagine to aspartate by PNAD renders the protein susceptible to arginylation, polyubiquitination and degradation as specified by the N-end rule. NTAN1 does not act on substrates with internal or C-terminal asparagines and does not act on glutamine residues in any position [, ].
