Human prostate-specific antigen: structural and functional similarity with serine proteases.
The complete amino acid sequence of the prostate-specific antigen (PA) from human seminal plasma has been determined from analyses of the peptides generated by cyanogen bromide, hydroxylamine, endoproteinases Arg-C and Lys-C. The single polypeptide chain of PA contains 240-amino acid residues and has a calculated Mr of 26,496. An N-linked carbohydrate side chain is predicted at asparagine-45, and O-linked carbohydrate side chains are possibly attached to serine-69, threonine-70, and serine-71. The primary structure of PA shows a high degree of sequence homology with other serine proteases of the kallikrein family. The active site residues of histidine, aspartic acid, and serine comprising the charge-relay system of typical serine proteases were found in similar positions in PA (histidine-41, aspartic acid-96, and serine-192). At pH 7.8, PA hydrolyzed insulin A and B chains, recombinant interleukin 2, and--to a lesser extent--gelatin, myoglobin, ovalbumin, and fibrinogen. The cleavage sites of these proteins by PA were chemically analyzed as the alpha-carboxyl side of some hydrophobic residues, tyrosine, leucine, valine, and phenylalanine, and of basic residues histidine, lysine, and arginine. The chymotrypsin-like activity of PA exhibited with the chromogenic substrate N-succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanine p-nitroanilide yielded a specific activity of 9.21 microM per min per mg of PA and Km and kcat values of 15.3 mM and 0.075s-1, respectively. "Trypsin-like" activity of PA was also detected with N alpha-benzoyl-DL-arginine p-nitroanilide and gave a specific activity of 1.98 microM per min per mg of PA. Protease inhibitors such as phenylmethylsulfonyl fluoride, diisopropyl fluorophosphate, L-1-tosylamido-2-phenylethyl chloromethyl ketone, aprotinin, leupeptin, soybean trypsin inhibitor as well as Zn2+ and spermidine were effective inhibitors of PA enzymatic activity.
K W
KW
Watt
P J
PJ
Lee
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M'Timkulu
W P
WP
Chan
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R
Loor
D000595:Amino Acid Sequence; D000941:Antigens; D010450:Endopeptidases; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D008297:Male; D010446:Peptide Fragments / Q000032:analysis; D011467:Prostate / Q000276:immunology*; D017430:Prostate-Specific Antigen; D012661:Semen / Q000032:analysis; D012697:Serine Endopeptidases
D000941:Antigens; D006023:Glycoproteins; D010446:Peptide Fragments; D010450:Endopeptidases; D012697:Serine Endopeptidases; D017430:Prostate-Specific Antigen