Displays aspartic proteolytic activity (PubMed:27872247). Together with A36, contributes to pollen and ovule development, including the apical cell wall constitution of the growing pollen tubes (PubMed:27872247). Displays punctate cytosolic localization and colocalizes with the GPI-anchored protein COBL10 at the plasma membrane and in the cytosol (PubMed:27872247). In pollen grains, mainly present at the plasma membrane and in reticular structures in the cytosol (PubMed:27872247). In pollen tubes, exhibits a punctate localization in the cytosol and occurs weakly at the plasma membrane (PubMed:27872247). Highly expressed in pollen and pollen tubes (PubMed:27872247). Mostly expressed in inflorescence, flowers and siliques, and barely in leaves and seedlings (PubMed:27872247). In flowers, expressed in the pollen and growing pollen tubes (PubMed:27872247). During microspore development, observed expressed from tetrad to tricellular pollen (PubMed:27872247). Also present in young siliques and developing ovules (PubMed:27872247). The double mutant a36 a39 produces inviable pollen which undergoes apoptosis-like programmed cell death, exhibits a compromised pollen tubes micropylar guidance and has degenerated female gametes (PubMed:27872247). The double mutant a36 a39 accumulates abnormally highly methylesterified homogalacturonans and xyloglucans in the apical pollen tube wall (PubMed:27872247). Belongs to the peptidase A1 family.