Palmitoyltransferase that catalyzes the addition of palmitate onto various protein substrates (PubMed:22031296). Palmitoylates sex steroid hormone receptors, including ESR1, PGR and AR, thereby regulating their targeting to the plasma membrane (PubMed:22031296). This affects rapid intracellular signaling by sex hormones via ERK and AKT kinases and the generation of cAMP, but does not affect that mediated by their nuclear receptor (PubMed:22031296). Palmitoylates FYN, regulates its localization in hair follicles and plays a key role in epidermal homeostasis and hair follicle differentiation. Through the palmitoylation of PLCB1 and the regulation of PLCB1 downstream signaling may indirectly regulate the function of the endothelial barrier and the adhesion of leukocytes to the endothelium. Also has a palmitoyltransferase activity toward ADRA1D, positively regulating its activity and expression and may thereby play a role in vascular contraction. May also palmitoylate eNOS and LCK (By similarity). . This is the function of ZDHHC21 (zDHHC palmitoyltransferase 21, Ensembl gene identifier ENSG00000175893).