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Biological activity of prostate‐specific antigen isolated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and electroelution

Human prostate‐specific antigen (PSA), a 33 kDa kallikrein‐like serine protease, occurring in the prostate, in seminal plasma and in blood, was prepared under nonreducing conditions in an enzymatically active form from seminal plasma by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), followed by fast copper staining, electroelution from gel slices and dialysis against isotonic phosphate‐buffered saline (PBS). Enzymatic activity was demonstrated for the first time directly by cleavage of semenogelin, one of the biological substrates of PSA, isolated by the same procedure, i.e. SDS‐PAGE and electroelution, but from seminal vesicle fluid. The purified PSA formed SDS‐stable complexes with the two major extracellular protease inhibitors in blood, α1‐antichymotrypsin (α1‐ACH) and α2‐macroglobulin (α2‐M). PSA isolated under reducing conditions was enzymatically inactive and could not bind to the protease inhibitors α1‐ACH and α2‐M.