Summary for peptidase C01.046: falcipain-2

Summary Alignment Sequences Sequence features Distribution Structure Literature Substrates Inhibitors Pharma

 

Names
MEROPS Namefalcipain-2
Other namesfalcipain-2A (Plasmodium falciparum), falcipain-2B (Plasmodium falciparum), FP2B protein (Plasmodium falciparum), vivapain-2 (Plasmodium vivax)
Name and HistoryFalcipains are papain homologues found in the malaria parasite Plasmodium. Falcipains -2 and -3 are components of the proteolytic machinery required for the degradation of host hemoglobin to amino acids. Until falcipain-2 could be purified, the properties of the different falcipains were confused in the literature, and properties assigned to 'falcipain' were subsequently shown to relate to falcipain-2 (Shenai et al., 2000).
Domain architecture
MEROPS Classification
Classification Clan CA >> Subclan (none) >> Family C1 >> Subfamily A >> C01.046
Holotypefalcipain-2 (Plasmodium falciparum) (peptidase unit: 260-484), MERNUM MER0012049
History Identifier created: MEROPS 5.3 (4 December 2000)
Activity
Catalytic typeCysteine
NC-IUBMBNot yet included in IUBMB recommendations.
Proteolytic eventsCutDB database (93 cleavages)
PreparationFalcipain-2 can be purified from P. falciparum trophozoites by affinity chromatography using Gly-Phe-Gly-Sepharose, to which neither falcipain-1 nor falcipain-3 bind (Shenai et al., 2000).
SpecificityFalcipain-2 is more active against peptides than proteins with a preference for Leu in P2 (Shenai et al., 2000). A substrate specificity study has shown preference for a hydrophobic residue in P2 with Leu most preferred, and Arg in P1 (Cotrin et al., 2013). Falcipain-2 also activates the plasmepsins, which are also important for hemoglobin degradation (Drew et al., 2008), and can release kinins from kininogen (Bagnaresi et al., 2012).
pH optimumFalcipain-2 is active in the pH range 5.0-6.5 (Shenai et al., 2000).
Inhibitor commentsIn addition to typical inhibitors of cysteine endopeptidases, falcipain-2 is inhibited by picomolar to low nanomolar concentrations of peptidyl fluoromethanes and vinyl sulfones containing the sequence Leu-homophenylalanine (Rosenthal et al., 1993, Olson et al., 1999). Falcipain-2 is potently inhited by its prodomain with a Ki 10-10 M(Sijwali et al., 2002). The naturally occuring inhibitor falstatin is expressed in stages other than trophozites, the hemoglobin-feeding stage, and controls falcipain activity outside of the food vacuole (Pandey et al., 2006).
StructureFalcipain-2 is a type II transmembrane protein with a membrane-spanning domain at the N-terminus. Unusually for a papain-like cysteine endopeptidase, the maturation cleavage site is lacking and mature falcipain-2 has an N-terminal extension of ~20 residues (Shenai et al., 2000). Tertiary structures have been solved for the enzyme in complex with inhibitors (Wang et al., 2006, Hogg et al., 2006, Kerr et al., 2009). The structures reveal two motifs unique to the falcipains, known as FP2nose, which mediated protein folding, and FP2arm, which interacts with hemoglobin.
LocationFalcipain-2 is a type II integral membrane protein located in the food vacuole (Shenai et al., 2000).
Biological aspectsFalcipain-2 activates plasmepsins (Drew et al., 2008), and both plasmepsins and falcipains -2, -2' and -3 are required for hemoglobin digestion in the food vacuole. Falcipain-2 is expressed earlier than other hemoglobin-degrading falcipains (Sijwali et al., 2004). Becasue falcipain-2 is able to cleave the erythrocyte cytoskeletal proteins ankyrin and protein 4.1 at neutral pH, a role in cell invasion has been proposed (Dua et al., 2001).
KnockoutKnockout of the falcipain-2 gene led to a transient block in hemoglobin digestion in trophozoites, with morphology returning to normal during the schizont stage (Sijwali et al., 2004).
Pharmaceutical relevanceAn siRNA study shows that falcipain-2 is of key importance in the escape of the merozoite of Plasmodium falciparum from the host erythrocyte by rupture of the membranes of parasitophorous vacuole and erythrocyte (Dasaradhi et al., 2005).
Contributing authorsNeil D. Rawlings, InterPro, Proteins Cluster, EMBL European Bioinformatics Institute, Hinxton, Cambridgeshire, CB10 1SD, UK
Cleavage site specificity Explanations of how to interpret the following cleavage site sequence logo and specificity matrix can be found here.
Cleavage pattern-/-/l/-Scissile bond-/-/-/- (based on 152 cleavages)
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Specificity matrix
 
Amino acid P4 P3 P2 P1 P1' P2' P3' P4'
Gly 10 7 4 11 8 11 9 10
Pro 10 9 2 2 3 14 12 8
Ala 14 18 8 16 24 18 12 19
Val 7 19 19 13 8 14 8 13
Leu 6 13 49 20 18 13 17 15
Ile 0 0 1 0 0 1 0 0
Met 2 5 5 1 2 2 1 1
Phe 9 6 11 7 13 9 9 7
Tyr 4 3 2 1 2 4 5 2
Trp 3 1 3 1 2 1 3 2
Ser 9 3 4 9 12 11 10 4
Thr 10 8 8 6 6 11 3 9
Cys 2 3 2 0 2 0 1 1
Asn 7 5 2 5 5 3 5 2
Gln 1 2 4 4 2 0 2 1
Asp 6 5 8 7 4 4 9 11
Glu 8 6 8 15 2 3 3 18
Lys 4 11 7 13 14 6 6 7
Arg 4 4 3 15 4 3 3 4
His 7 4 2 6 9 14 12 6
Specificity from combinatorial peptides
 
Organism comment P4 P3 P2 P1 P1' P2' P3' P4' optimal substrate fluorophore or acceptor-donor pair Reference
Plasmodium falciparum recombinant broad L L R/K - - - - broad-LLR AMC Ramjee et al., 2006
Plasmodium falciparum recombinant H/N/broad R/broad L R/K - - - - HRLR ACC Subramanian et al., 2009
Plasmodium falciparum recombinant - - L R F - - - xxLR+Fxxx Abz-Tyr(NO2) Ramjee et al., 2006