Probable catalytic subunit of the gamma-secretase complex, an endoprotease complex that catalyzes the intramembrane cleavage of integral membrane proteins such as Notch receptors (lin-12 or glp-1). Provides the major presenilin function compared to hop-1 and spe-4. Required cell-autonomously for correct neurite connectivity of the AIY cholinergic interneurons and their correct functioning in thermotaxis. Required for mesodermal patterning of muscle function. Promotes basement membrane gap formation during tissue remodeling (PubMed:27661254). Homodimer. Component of the gamma-secretase complex, a complex probably composed of the presenilin homodimer (sel-12, hop-1 or spe-4), nicastrin (aph-2), aph-1 and pen-2 (Probable). Interacts with sel-10 (PubMed:9861048). Expressed in most neurons. Expressed both maternally and zygotically. Ubiquitously expressed throughout the development and in the adult. The PAL motif is required for normal active site conformation. Belongs to the peptidase A22A family.