The function of MBOAT4 (membrane bound ghrelin O-acyltransferase MBOAT4, ENSG00000177669) is as follows. Catalyzes ghrelin acylation at 'Ser-3' using preferentially octanoyl-CoA, hexanoyl-CoA and decanoyl-CoA as acyl-CoA donors leading to ghrelin activity (PubMed:18443287, PubMed:24045953, PubMed:25562443, PubMed:28134508). In vitro also uses acyl-CoA donors of different lengths from short-chain (C2) to long-chain fatty acids (C16) knowing that acyl-CoA donors from butanoyl-CoA (C4) to dodecanoyl-CoA (C12) are more efficient compared to longer acyl-CoA donors, such as myristoyl- CoA (C14) and palmitoyl-CoA (C16) that are not efficient (PubMed:18443287). {ECO:0000269|PubMed:18443287, ECO:0000269|PubMed:24045953, ECO:0000269|PubMed:25562443, ECO:0000269|PubMed:28134508}.