Synthesis of N alpha-[3H]acetyl-L-lysine chloromethyl ketone and its use in the fluorographic detection of proteases

Biotinylated aprotinin: a versatile probe for the detection of serine proteinases on western blots

The present study was undertaken to provide a highly sensitive detection system for the identification and characterisation of serine proteinases separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Biotinylated aprotinin of high specific activity (88-92% active) was prepared (i) by reaction of aprotinin directly with N-hydroxy sulfosuccinimidyl-6-(biotinamido) hexanoate, and (ii) by reaction of aprotinin-trypsin complex with N-hydroxy succinimidobiotin. Both biotinylated aprotinin samples were suitable as probes for the detection of the serine proteinases, neutrophil elastase and cathepsin G, pancreatic trypsin and chymotrypsin and plasmin on nitrocellulose blots. Specific irreversible chloromethyl ketone proteinase inhibitors used in combination with this detection system enabled respective proteinases to be selectively inactivated and thus positively identified. The biotinylated aprotinin detection system was highly sensitive and could detect as little as 0.2 ng (8.5 fmol) of active proteinase (trypsin). In summary, a method has been developed for the sensitive detection of serine proteinases separated by SDS-PAGE. The method is more sensitive and convenient to perform than conventional zymography and significantly, when used in conjunction with specific serine proteinase inhibitors or specific antibodies can yield appreciable information on the identity of the respective serine proteinases being examined. Furthermore the molecular mass of the serine proteinase may be reliably obtained by this method. This method should find application in identifying the role that serine proteinases play in the etiopathogenesis of connective tissue disorders.

The multiple forms of trypsin-like activity present in various strains of Porphyromonas gingivalis are due to the presence of either Arg-gingipain or Lys-gingipain

Porphyromonas gingivalis contains high concentrations of numerous cysteine proteinases with trypsin-like activity which have been implicated as important virulence factors in adult-onset periodontitis. We have analyzed the subfractions of six P. gingivalis strains for the presence of arginine-X- and lysine-X-specific proteinases (Arg-gingipain [RGP] and Lys-gingipain [KGP]) previously purified from P. gingivalis H66. Western blot (immunoblot) analysis using antibodies produced against RGP and the N-terminal peptides of RGP or the catalytic subunit of KGP indicated that these enzymes are synthesized by the strains studied and exist as multiple molecular mass species. The major forms of RGP were identified as 110-, 95-, 70- to 90-, and 50-kDa proteins, the first two being a complex of the 50-kDa catalytic subunit with hemagglutinins, with or without an added membrane anchorage peptide. The other forms are single-chain enzymes. While the 95- and 50-kDa RGP were found predominantly in culture medium, the 110- and 70- to 90-kDa forms associated with membranous fractions of the bacteria. The predominant form of KGP in all strains was a complex of the 60-kDa catalytic domain with hemagglutinins, and vesicle- and membrane-associated KGP was about 15 kDa larger than the 105-kDa enzyme present in culture media. These data explain the apparent complexity of P. gingivalis proteinases and indicate that in all strains tested there are two identical enzymes, one with arginine-X specificity and the other with lysine-X specificity, which, working in concert, are responsible for the trypsin-like activity associated with this bacterium.