METAP1 encodes methionyl aminopeptidase 1, which cotranslationally removes the N-terminal methionine from nascent proteins when the second residue is small and uncharged 1. The enzyme forms a multienzyme complex with NAC (nascent polypeptide-associated complex) and NatA (N-acetyltransferase A) during translation, where NAC recruits METAP1 to ribosomes using a flexible tail and positions it for efficient methionine excision 12. This cotranslational processing is essential for approximately 40% of the mammalian proteome and is required for normal cell cycle progression 1. METAP1 works cooperatively with other enzymes including NatD for histone H2A and H4 modification and exchanges with NMT1 for protein N-myristoylation 34. Disease relevance includes preeclampsia, where increased METAP1 expression in endothelial cells correlates with decreased angiogenesis and increased proinflammatory gene expression 5. METAP1 deletion results in increased methionine retention, particularly for Met-Ser, Met-Pro, and Met-Ala starting proteins, and affects cellular proliferation rates, indicating MetAP1 has higher activity than MetAP2 for certain substrates 6. The enzyme also participates in zinc-mediated gut barrier function through the ZNG1-METAP1-PRMT5 pathway 7.