Might form homotrimers; these trimers are only formed in retina. Widely expressed, including in retina and brain (at protein level), as well as in kidney, testis and ovary. Expressed in all layers of the retina, including inner segments of photoreceptor cells and ganglion cells (at protein level). In the developing eye, already detected at 10.5 dpc. Expression increases from 12.5 though 18.5 dpc in all retinal cells (at protein level). At P1, expressed in a small number of cells at the level of the ganglion cell layer and in the inner edge of the ventricular zone of the retina. The number of expressing cells increases and, by P8 to P11, entirely occupies the ganglion cell layer and inner nuclear layer. At that stage, not detected in the photoreceptor cell bodies of the outer nuclear layer. At P21, expressed in all nuclear layers of the retina, including cones (at protein level). Belongs to the peptidase S54 family. Although strongly related to the peptidase S54 family, it lacks the conserved active sites, suggesting that it has no peptidase activity.