Updated PubMed. Protein acetylation is a universally conserved modification occurring on N-termini (N--acetylation, NTA) and on internal lysines residues (-lysine-acetylation, KA). So far, NTA and KA were known to be supported by distinct families of enzymes (NATs and KATs, respectively), despite most of them share a common GCN5-related N-acetyltransferase (GNAT) domain. Although recent reports indicate that both NTA and KA occur frequently in plant plastids, little is known about the machinery involved in plastid acetylations and why these modifications are that frequent in this organelle. Searches for new putative NAT and KAT genes in Arabidopsis thaliana illuminate a common pool of ten putative candidates, displaying a number of unique features both at the level of conserved key residues and motifs. Here, we show that eight out of the ten candidates are associated with the plastids. In vivo investigation based on global quantitative mass spectrometry of these enzymes revealed that they exhibit a number of unique features, supporting both NAT and KAT activities of the plastids. All identified enzymes show distinct KAT substrate specificity and display unexpected relaxed NAT substrate specificity, each with differences in terms of NTA yields and preferred substrates. Together, this study reveals an unexpected multitasking protein modification machinery dedicated to the plastids of plant. We suggest that this machinery likely evolved to support specific needs of this organelle.