Detection of human glandular kallikrein, hK2, as its precursor form and in complex with protease inhibitors in prostate carcinoma serum.

Forms of human glandular kallikrein (kK2) in prostate carcinoma serum were identified using monoclonal antibodies specific for hK2 and prohK2. Recombinant mammalian hK2, prohK2, and prostate = specific antigen (PSA) were utilized to confirm the specificity of monoclonal antibodies for hK2 and the lack of reactivity with PSA. In prostate cancer patient sera containing high levels of hK2 (>100 ng/ml), hK2 exists as a complex with alpha1-antichymotrypsin with a molecular weight of 90 kDa. The kallikrein also exists as a 32-kDa free form, which includes the precursor pro form of hK2. The relative amount of complex and free hK2 varied, but in most sera examined the 32-kDa form predominated. Recombinant hK2 readily formed complexes with alpha2-macroglobulin when the two proteins were incubated together as well as when hK2 was spiked into female serum.