KLK6(Kallikrein-related peptidase 6), also called KALLIKREIN 6, NEUROSIN, PROTEASE M, ZYME or PRSS9, is a protein that in humans is encoded by the KLK6 gene. This gene is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19. The encoded enzyme is regulated by steroid hormones. Northern blot analysis revealed that the PRSS9 mRNA was expressed in several primary tumors and cell lines from mammary, prostate, and ovarian cancers, but was not detected in any metastases of these cancers. The KLK6 gene is mapped on 19q13.41. In tissue culture, the enzyme has been found to generate amyloidogenic fragments from the amyloid precursor protein, suggesting a potential for involvement in Alzheimer's disease. Upon cellular stress, neurosin was released from mitochondria to the cytosol, which resulted in the increase of degraded alpha-synuclein species. Neurosin may play a significant role in physiologic alpha-synuclein degradation and also in the pathogenesis of synucleinopathies.