Recombinant Mouse Protein N-terminal asparagine amidohydrolase (Ntan1)

Introduction to Recombinant Mouse Protein N-terminal Asparagine Amidohydrolase (Ntan1)

Recombinant Mouse Protein N-terminal asparagine amidohydrolase, commonly referred to as Ntan1, is an enzyme that plays a crucial role in the ubiquitin-dependent N-end rule pathway of protein degradation. This pathway links the in vivo half-life of a protein to the identity of its N-terminal residue. Ntan1 specifically catalyzes the deamidation of N-terminal L-asparagine (Asn) residues, converting them into aspartate (Asp), which is a secondary destabilizing residue. This process is essential for marking proteins for degradation via the proteasome pathway.

Function and Mechanism

Ntan1 is highly selective for N-terminal peptidyl L-Asn and does not deamidate free L-Asn, L-Gln, N-terminal peptidyl L-Gln, or acetylated N-terminal peptidyl L-Asn . The enzyme requires a critical cysteine residue for its catalytic activity, as demonstrated by the loss of activity in mutants where this cysteine is replaced . The N-end rule pathway involves several steps, starting with the deamidation of N-terminal Asn or Gln residues, followed by their conjugation to arginine, which is recognized by specific E3 ubiquitin ligases, leading to protein degradation .

Genetic Studies in Mice

Studies involving mice deficient in Ntan1 have shown that these mice exhibit altered behaviors, including changes in spontaneous activity, spatial memory, and social behavior . Despite lacking Ntan1 activity, these mice are fertile and appear normal externally. The absence of Ntan1 leads to the stabilization of proteins with N-terminal Asn, as they cannot be efficiently marked for degradation .

Biochemical Characterization

The biochemical characterization of Ntan1 involves its expression in bacterial systems, such as E. coli, where it is purified and studied for its enzymatic properties. The enzyme's activity is influenced by its N-terminal structure, with the exposure of a conserved proline residue enhancing its catalytic efficiency .

Physiological Roles

Ntan1 plays a role in various physiological processes, including protein turnover, which is crucial for maintaining cellular homeostasis. Its involvement in the N-end rule pathway suggests it could be important in regulating protein stability in response to cellular signals or stress conditions .

Table 1: Enzymatic Properties of Ntan1

Table 2: Effects of Ntan1 Deficiency in Mice

References Expression and biochemical characterization of the human enzyme N-terminal asparagine amidohydrolase (NTAN1). Expression and biochemical characterization of the human enzyme N-terminal asparagine amidohydrolase (NTAN1). Altered activity, social behavior, and spatial memory in mice lacking the NTAN1p amidase and the asparagine branch of the N-end rule pathway. Gene Result: NTAN1 N-terminal asparagine amidase [Homo sapiens]. A cellular assay system revealed the deamidase-mediated regulation of the Arg/N-end rule pathway.