Families and clans of cysteine peptidases
ABSTRACT The known cysteine peptidases have been classified into 35 sequence families. We argue that these have arisen from at least five separate evolutionary origins, each of which is represented by a set of one or more modern-day families, termed a clan. Clan CA is the largest, containing the papain family, C1, and others with the Cys/His catalytic dyad. Clan CB (His/Cys dyad) contains enzymes from RNA viruses that are distantly related to chymotrypsin. The peptidases of clan CC are also from RNA viruses, but have papain-like Cys/His catalytic sites. Clans CD and CE contain only one family each, those of interleukin-1-converting enzyme and adenovirus L3 proteinase, respectively. A few families cannot yet be assigned to clans. In view of the number of separate origins of enzymes of this type, one should be cautious in generalising about the catalytic mechanisms and other properties of cysteine peptidases as a whole. In contrast, it may be safer to generalise for enzymes within a single family or clan.
- Studies in Surface Science and Catalysis - STUD SURF SCI CATAL. 01/1997; 105:997-1004.
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ABSTRACT: Proteolytic degradation of barley proteins is examined in green (unkilned) malt and germinating seeds from Hordeum vulgare L. cv. Harrington. Zymographic analysis of the Harrington green malt extracts using commercial preparations of barley beta-amylase incorporated as a proteolytic substrate in 2-D SDS gels shows multiple proteolytic activities. A developmental study shows that the several green malt beta-amylase-degrading activities appear at around day 2 of germination. The several activities appear to increase and decrease through 7 days of germination in a coordinated fashion. Gels treated with class-specific proteinase inhibitors show that serine-class proteinase activities are responsible for barley beta-amylase degradation seen on the zymograms. Western blot analysis also shows that proteolytic enzymes recovered from 1-D electrophoretic gels degrade barley beta-amylase, and that the degradation is inhibited by PMSF. This is the first demonstration that malt proteinases are capable of degrading important metabolic enzymes in germinating barley, and the first postulated physiological role for the serine class proteinases in barley malt.Journal of Cereal Science 05/2008; · 2.09 Impact Factor
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ABSTRACT: TRAIL (APO-2 ligand) and CD95L (CD95/APO-1/Fas ligand) share the highest homology among the TNF family members and the ability to induce apoptosis. These similarities raise the issue of a potential functional redundancy between the two ligands. We have previously shown that CD95L-resistant cells may be sensitive to TRAIL, even though apoptosis induced by both ligands is blocked by caspase inhibitors. Here we investigated TRAIL protein expression in cells of T and B origin and compared its regulation of expression with that of CD95L. A rabbit antibody (Ab) to a peptide sequence in the extracellular region of TRAIL identified recombinant TRAIL (rTRAIL) produced by Sf9 cells as a protein of approximately 32-33 kDa and soluble rTRAIL as a 19-20-kDa protein. In human and mouse cells, the Ab identified a 33-34-kDa and an additional 19-20-kDa protein only in human cells. Both transformed cells of the T and B lymphocyte lineage were found to react with the anti-TRAIL Ab by immunoblot analysis and surface staining. The majority of the cells analyzed co-expressed TRAIL and CD95L. Two cell lines showed a mirror-pattern, one being TRAILhigh CD95Llow and the other TRAILlow CD95Lhigh, thus suggesting the existence of a cell type-specific regulation of expression of the two ligands. Differently from CD95L, surface TRAIL was not up-regulated by any of the metalloprotease inhibitors tested, independently of the cell type analyzed. Conversely, reactivity with the anti-TRAIL but not with the anti-CD95L Ab was enhanced by cysteine protease inhibitors. An in vitro cleavage assay showed that generation of soluble rTRAIL was dependent on the functional activity of cysteine proteases, as it was blocked by leupeptin and E64 but not by the metalloprotease inhibitor 1,10-phenanthroline. Thus, even though TRAIL and CD95L share structural and functional properties, they have unique properties as they differ in their regulatory pathways, i.e. cell-type-dependent expression and sensitivity to protease inhibitors.European Journal of Immunology 03/1998; 28(3):973-82. · 4.97 Impact Factor