Key regulator of the Wnt signaling pathway that mediates lipid modification of Wnt proteins (PubMed:10444600, PubMed:15020416, PubMed:9288750). Acts as a protein-serine O-palmitoleoyltransferase that catalyzes the attachment of palmitoleate, a 16-carbon monounsaturated fatty acid (C16:1), to Wnt proteins (By similarity). Serine palmitoleylation of WNT proteins is required for efficient binding to frizzled receptors (By similarity). Has a role in cell specification, specifically in blastomere signaling (PubMed:10444600, PubMed:15020416, PubMed:9288750). Involved in cytosketetal polarity (PubMed:10444600, PubMed:15020416, PubMed:9288750). Required for the orientation of mitotic spindle axis (PubMed:9288749, PubMed:10444600, PubMed:15020416, PubMed:9288750). (9Z)-hexadecenoyl-CoA + [Wnt protein]-L-serine = [Wnt protein]-O-(9Z)-hexadecenoyl-L-serine + CoA Embryonic lethal with severely defective embryonic morphogenesis with no endoderm and excess mesoderm. In addition, embryos have defective mitotic spindle orientation in the 8-cell stage ABar blastomere. Belongs to the membrane-bound acyltransferase family. Porcupine subfamily.