Jm. Duffy et al., THE DETECTION, QUANTIFICATION AND PARTIAL CHARACTERIZATION OF CATHEPSIN B-LIKE ACTIVITY IN HUMAN PATHOLOGICAL SYNOVIAL-FLUIDS, European journal of clinical chemistry and clinical biochemistry, 32(6), 1994, pp. 429-434
In this study, the levels of the cysteine proteinase - cathepsin B wer
e measured in diseased synovial fluids using a steady state fluorometr
ic assay. Cathepsin B-like activity was shown to be present in all the
samples analysed, with the rheumatoid arthritic synovial fluids posse
ssing significantly higher concentrations (mean value ca. 416 mg/1) th
an the osteoarthritic fluids (mean value ca. 142.4 mg/1). In addition,
upon treatment with pepsin, all of the rheumatoid arthritis samples w
ere shown to possess additional cathepsin B-like activity, suggesting
the presence of a reservoir of latent precursor molecules. By utilisin
g a recently developed biotinylated affinity label for cathepsin B-lik
e proteinases and sheep anti-(human cathepsin B) antibodies, used in c
ombination with SDS-PAGE and Western blotting, the rheumatoid arthriti
c synovial cathepsin B was shown to exist in two forms with apparent m
olecular masses of M(r) 29 000 and 42 000. We propose that the former
is a functionally active proteinase, whereas the latter is a pepsin ac
tivatable proform which, when cleaved by this aspartyl proteinase, is
converted into a catalytically competent species of M(r) 20 000.