HHAT (hedgehog acyltransferase) is a multipass transmembrane enzyme that catalyzes N-terminal palmitoylation of hedgehog proteins, primarily Sonic Hedgehog (SHH) and Desert Hedgehog (DHH), a modification critical for hedgehog signaling 12. HHAT contains 10 transmembrane domains and functions as a member of the membrane-bound O-acyltransferase (MBOAT) family 2. The enzyme transfers palmitoyl-CoA from the cytoplasmic side to the luminal side of the endoplasmic reticulum membrane, where palmitoylation occurs 34. Cryo-EM structures reveal that HHAT contains a heme group essential for catalytic function and employs an active site that bridges opposite membrane surfaces to facilitate acyl chain transfer 34. HHAT is essential for proper embryonic development and testicular organogenesis 2. Pathogenic variants in HHAT are associated with 46,XY disorders of sex development (DSD) and gonadal dysgenesis, indicating its critical role in sexual development 56. Additionally, HHAT's role in hedgehog signaling makes it therapeutically relevant in cancer, with selective HHAT inhibitors showing potential as anti-cancer agents 7.