Catalytic subunit of the N-terminal acetyltransferase C (NatC) complex (PubMed:19398576, PubMed:37891180). Catalyzes acetylation of the N-terminal methionine residues of peptides beginning with Met-Leu-Ala and Met-Leu-Gly (PubMed:19398576, PubMed:37891180). N- terminal acetylation protects proteins from ubiquitination and degradation by the N-end rule pathway (PubMed:37891180). Necessary for the lysosomal localization and function of ARL8B sugeesting that ARL8B is a NatC substrate (PubMed:19398576). {ECO:0000269|PubMed:19398576, ECO:0000269|PubMed:37891180}. This is the function of NAA30 (N-alpha-acetyltransferase 30, NatC catalytic subunit, ENSG00000139977).