Major secreted protein that belongs to the subtilisin family serine proteases. Hydrolysis of proteins with broad specificity for peptide bonds, and a preference for a large uncharged residue in P1. Hydrolyzes peptide amides. The protease activity is completely inhibited by the serine inhibitor PMSF but is not affected by thiol group inhibitors and in the presence of dithiothreitol (PubMed:6750031). In the presence of high concentrations of o-phenanthroline the protease activity is only partially inhibited (PubMed:6750031). The pro-region plays an inhibitory role and may provide a mechanism for preventing premature activation in the secretory pathway (PubMed:2649495). Optimum pH is 9.0-10.0. Optimum temperature is 40 degrees Celsius. Proper secretion requires TSR1. Expression is subject to at least 3 different regulatory controls, carbon, sulfur and nitrogen repression (PubMed:870075). Intracellular cysteine and ammonia appear to be the metabolic signals for sulfur and nitrogen repression (PubMed:870075). Moreover, pH regulates expression independently from other metabolic signals, with highest levels of AEP mRNA at pH 6.5 (PubMed:8842151, PubMed:9308186). The transcriptional activator RIM101 and the Rim pathway are required for the alkaline induction of gene expression (PubMed:9199331, PubMed:11861549). Two major upstream activation sequences (UASs) are essential for promoter activity under conditions of repression or full induction. The distal UAS (UAS1) is located at position -790 to -778, whereas the proximal UAS (UAS2) localizes at positions -148 to -124 (PubMed:8264600, PubMed:10206713). The pro-region is removed through cleavage by XPR6 after Lys156-Arg157, which yields mature active XPR2. The 10 consecutive -X-Ala- or -X-Pro- dipeptides located over 100 amino acids upstream of the N-terminal of mature XPR2 are subject to dipeptidyl aminopeptidase (DPAPase)-processing (PubMed:9353927). DPAPase activity is not necessary for XPR6 cleavage and for secretion of mature active XPR2 (PubMed:9353927). N-glycosylated. Glycosylation within the pro-region has no effect on secretion and maturation at 18 degrees Celsius, but is required for secretion at 28 degrees Celsius (PubMed:1995632). The pro-region inhibits protease activity (PubMed:2649495) and plays an additional essential role in the proper folding of the protein into a conformation compatible with secretion (PubMed:1995632, PubMed:1634541). Its complex processing and high level of secretion make XPR2 the perfect model to study the secretion pathway. Belongs to the peptidase S8 family. Strain CLIB 122 / E 150 has a defective XPR2 sequence (xpr2-322) which lacks the N-terminus (positions 1 to 34).