Purification and characterization of alkaline phosphatase from human seminomas.

Despite the apparent link between the presence of alkaline phosphatase (ALP) and various cancers, it has so far been difficult to determine distinct differences between seminoma-derived ALP and placental ALP (PLAP). In order to determine specificity, we purified ALP from a seminoma type of human testicular cancer tissue and compared its biochemical and immunological properties with those of PLAP. The purified ALP had a specific activity of 66 units per mg of protein, and it was possible to obtain 169 microg of purified preparation from 60 g of tissue. The molecular weight of the purified seminoma enzyme was approximately 500 kDa. We found that a novel type of ALP from human testicular cancer tissue exists, with a high molecular weight and differing in degree, from the seminoma ALP previously reported.