Highly expressed in hydatidiform moles, but barely expressed in dermoid cysts. Biallelic expression is detected in blood lymphocytes. Seems to imprinted in an isoform-specific manner rather than in a tissue-specific manner in lymphocytes. Isoform 1 is expressed only from the paternal allele. Isoform 2 is expressed from both the paternal allele and the maternal allele. Monoallelic expression of paternally derived allele was observed in all fetal tissues examined, including brain, skeletal muscle, kidney, adrenal, tongue, heart, skin and placenta. In 75-day fetus, expressed in the amnion, brain, heart, lung, stomach, gut, adrenal, kidney, muscle and liver. Belongs to the AB hydrolase superfamily.