NAA20 encodes the catalytic subunit of the NatB complex, which catalyzes N-terminal acetylation of approximately 20% of the human proteome 1. The enzyme specifically acetylates proteins beginning with Met-Asp, Met-Glu, Met-Asn, and Met-Gln sequences 1. NAA20 functions as part of a heterodimeric complex with the auxiliary subunit NAA25, which is essential for enzymatic activity and increases substrate affinity 2. The NatB complex operates co-translationally and is highly conserved across eukaryotes 2. Disease-wise, biallelic missense variants in NAA20 cause autosomal recessive intellectual developmental disorder characterized by developmental delay, intellectual disability, and microcephaly 13. These pathogenic variants impair NatB complex formation and reduce catalytic activity toward substrates 1. Beyond developmental roles, NAA20 contributes to cancer progression by regulating the LKB1-AMPK-mTOR signaling axis in hepatocellular carcinoma 4. The enzyme also plays crucial roles in cell cycle regulation and DNA replication initiation, with depletion leading to senescence 5. Additionally, NAA20-mediated N-terminal acetylation protects alpha-synuclein from proteasomal degradation, suggesting therapeutic relevance for Parkinson's disease 6.