Heterodimer with the iron-binding acid phosphatase, UF. Levels in the endometrium increase as pregnancy proceeds, reaching maximal levels around day 70 and then remain relatively constant in late gestation (days 70-110). By progesterone. A series of at least four post-translational proteolytic processing steps and differential N-linked glycosylation generate various molecular forms. Three mature forms starting at positions 41, 45 and 100 are produced. Glycosylated; contains the so-called mannose 6-phosphate lysosomal recognition marker. The UFAP are a group of three (MW 42 kDa, 48 kDa, and 50 kDa) antigenically related, basic glycoproteins secreted by the porcine uterus. Belongs to the serpin family. UTMP subfamily.