Internally repeated sequences in ras gene products

Role of cysteine endopeptidases in cancerogenesis

Role of cysteine endopeptidases in cancerogenesis steps: neoplastic transformation, invasion and metastasis is reviewed and discussed. Positive correlation between tumor invasiveness, as well as its metastatic potential and secretion of cysteine endopeptidase (particularly cathepsins B and L) has been documented well in literature. Based on our recent results we postulate that serum endopeptidase-like activity could be used as a marker of cancer aggressiveness in diagnostic procedures in oncology. We also propose that the cysteine endopeptidase inhibitor levels (total, active and latent) could be useful factors for recognising the activation of the organism self-defence mechanisms against cancer. In addition, our idea of use of urinary cysteine peptidase inhibitors (UCPI) as potential anticancer agents is presented and discussed.

Brain cysteine proteinase inhibitors II: evidence that a 21-kDa papain-binding component resembles ras p21

A 21-kDa protein extracted from rat or bovine brain at high pH was purified on alkylated-papain and shown to have dual ras-like and cysteine proteinase inhibitory (CPI) properties. This was demonstrated by its GTP-binding activity, cross-reactivity toward pan-reactive ras p21 monoclonal antibody, and inhibition of papain. The material eluted earlier than cystatins or kininogens on the alkylated papain-affinity column and was devoid of other CPIs based on immunoblot analysis. In a second procedure, ras p21s isolated from rat or bovine brain membranes by cholate extraction and purified by gel-permeation and hydrophobic interaction were shown to act also as potent CPIs, inhibiting rat brain cathepsin L, papain, or rat brain cathepsin B with Ki values of 3, 11, and 167 nM, respectively. This component cross-reacted with the monospecific anti-ras, but not with other anti-CPIs, and represented 3-4% of total GTP binding present in homogenates. The specific activity of the purified 21 kDa component was 4.7 nmol GTP-gamma-S bound per mg protein. The data support the notion that brain ras p21s constitute a separate group of CPIs and are available for regulating some aspects of brain protein turnover.