Molecular cloning of a novel human acid phosphatase gene (ACPT) that is highly expressed in the testis

Acid phosphatases are enzymes capable of hydrolyzing orthophosphoric acid e sters in an acid medium. Prostatic acid phosphatase has served as a tumor m arker for metastatic prostate cancer for many years. We have cloned a new h uman acid phosphatase gene (named testicular acid phosphatase, ACPT), which is expressed mainly in testis and to a lower extent in the prostate, trach ea, and other tissues. This gene maps to chromosome 19q13.4, in an area tha t harbors many cancer-related genes. The testicular acid phosphatase gene i s composed of 11 exons, and the protein is predicted to have a luminal doma in, a transmembrane domain, and a cytoplasmic domain. The N-terminal end of the protein encodes a signal peptide. The protein has approximately 50% ho mology with both the prostatic and the lysosomal acid phosphatases, and the position of the cysteine residues, the N-glycosylation sites, and the hist idine catalytic site are conserved among the three proteins. The testicular acid phosphatase gene is up-regulated by androgens and is down-regulated b y estrogens in the prostate cancer cell line LNCaP. Our preliminary results indicate that this gene exhibits a lower level of expression in testicular cancer tissues than in their normal counterparts. (C) 2001 Academic Press.