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Hydrolase/hydrolase inhibitor PDB id
Protein chain
212 a.a. *
Waters ×32
* Residue conservation analysis
PDB id:
Name: Hydrolase/hydrolase inhibitor
Title: Binding of chloromethyl ketone substrate analogues to crysta papain
Structure: Papain. Chain: a. Engineered: yes. Acetyl-ala-ala-phe-ala-chloromethylketone inhibit chain: i. Synonym: acaapack. Engineered: yes
Source: Carica papaya. Papaya. Organism_taxid: 3649. Tissue: fruit latex. Synthetic: yes
Biol. unit: Dimer (from PQS)
2.80Å     R-factor:   not given    
Authors: J.Drenth,K.H.Kalk,H.M.Swen
Key ref:
J.Drenth et al. (1976). Binding of chloromethyl ketone substrate analogues to crystalline papain. Biochemistry, 15, 3731-3738. PubMed id: 952885 DOI: 10.1021/bi00662a014
01-Nov-76     Release date:   12-Apr-77    
Supersedes: 2pap
Go to PROCHECK summary

Protein chain
Pfam   ArchSchema ?
P00784  (PAPA1_CARPA) -  Papain
345 a.a.
212 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 3 residue positions (black crosses)

 Enzyme reactions 
   Enzyme class: E.C.  - Papain.
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: Hydrolysis of proteins with broad specificity for peptide bonds, with preference for a residue bearing a large hydrophobic sidechain at the P2 position. Does not accept Val at P1'.
 Gene Ontology (GO) functional annotation 
  GO annot!
  Biological process     proteolysis   1 term 
  Biochemical function     cysteine-type peptidase activity     1 term  


DOI no: 10.1021/bi00662a014 Biochemistry 15:3731-3738 (1976)
PubMed id: 952885  
Binding of chloromethyl ketone substrate analogues to crystalline papain.
J.Drenth, K.H.Kalk, H.M.Swen.
Papain (EC is a proteolytic enzyme, the three-dimensional structure of which has been determined by x-ray diffraction at 2.8 A resolution (Drenth, J., Jansonius, J.N., Koekoek, R., Swen, H. M., and Wothers, B.G. (1968), Nature (London) 218, 929-932). The active site is a groove on the molecular surface in which the essential sulfhydryl group of cysteine-25 is situated next to the imidazole ring of histidine-159. The main object of this study was to determine by the difference-Fourier technique the binding mode for the substrate in the groove in order to explain the substrate specificity of the enzyme (P2 should have a hydrophobic side chain (Berger and Schechter, 1970) and to contribute to an elucidation of the catalytic mechanism. To this end, three chloromethyl ketone substrate analogues were reacted with the enzyme by covalent attachment to the sulfur atom of cysteine-25. The products crystallized isomorphously with the parent structure that is not the native, active enzyme but a mixture of oxidized papain (probably papain-SO2-) and papain with an extra cysteine attached to cysteine-25. Although this made the interpretation of the difference electron density maps less easy, it provided us with a clear picture of the way in which the acyl part of the substrate binds in the active site groove. The carbonyl oxygen of the P1 residue is near two potential hydrogen-bond donating groups, the backbone NH of cysteine-25 and the NH2 of glutamine-19. Valine residues 133 and 157 are responsible for the preference of papain in its substrate splitting. By removing the methylene group that covalently attaches the inhibitor molecules to the sulfur atom of cysteine-25 we obtained acceptable models for the acyl-enzyme structure and for the tetrahedral intermediate. The carbonyl oxygen of the P1 residue, carrying a formal negative charge in the tetrahedral intermediate, is stabilized by formation of two hydrogen bonds with the backbone NH of cysteine-25 and the NH2 group of glutamine-19. This situation resembles that suggested for the proteolytic serine enzymes (Henderson, R., Wright, C. S., Hess, G. P., and Blow, D. M. (1971), Cold Spring Harbor Symp. Quant. Biol. 36, 63-70; Robertus, J. D., Kraut, J., Alden, R. A., and Birktoft, J. J. (1972b), Biochemistry 11, 4293-4303). The nitrogen atom of the scissile peptide bond was found close to the imidazole ring of histidine-159, suggesting a role for this ring in protonating the N atom of the leaving group (Lowe, 1970). This proton transfer would be facilitated by a 30 degrees rotation of the ring around the C beta-Cgamma bond from an in-plane position with the sulfur atom to an in-plane position with the N atom. The possibility of this rotation is derived from a difference electron-density map for fully oxidizied papain vs. the parent protein.

Literature references that cite this PDB file's key reference

  PubMed id Reference
21244636 N.Zhang, R.Zhong, H.Yan, and Y.Jiang (2011).
Structural features underlying selective inhibition of GSK3β by dibromocantharelline: implications for rational drug design.
  Chem Biol Drug Des, 77, 199-205.  
21245344 T.W.James, N.Frias-Staheli, J.P.Bacik, J.M.Levingston Macleod, M.Khajehpour, A.García-Sastre, and B.L.Mark (2011).
Structural basis for the removal of ubiquitin and interferon-stimulated gene 15 by a viral ovarian tumor domain-containing protease.
  Proc Natl Acad Sci U S A, 108, 2222-2227.
PDB codes: 3pse 3pt2
20014086 B.Knuckley, C.P.Causey, P.J.Pellechia, P.F.Cook, and P.R.Thompson (2010).
Haloacetamidine-based inactivators of protein arginine deiminase 4 (PAD4): evidence that general acid catalysis promotes efficient inactivation.
  Chembiochem, 11, 161-165.  
20383756 C.X.Chen, B.Jiang, E.A.Carrey, and L.M.Zhu (2010).
Reduction of benzaldehyde catalyzed by papain-based semisynthetic enzymes.
  Appl Biochem Biotechnol, 162, 1506-1516.  
19455353 S.A.Trejo, L.M.López, N.O.Caffini, C.L.Natalucci, F.Canals, and F.X.Avilés (2009).
Sequencing and characterization of asclepain f: the first cysteine peptidase cDNA cloned and expressed from Asclepias fruticosa latex.
  Planta, 230, 319-328.  
17879947 I.Frydrych, and P.Mlejnek (2008).
Serine protease inhibitors N-alpha-tosyl-L-lysinyl-chloromethylketone (TLCK) and N-tosyl-L-phenylalaninyl-chloromethylketone (TPCK) are potent inhibitors of activated caspase proteases.
  J Cell Biochem, 103, 1646-1656.  
18980241 I.Frydrych, and P.Mlejnek (2008).
Serine protease inhibitors N-alpha-tosyl-L-lysinyl-chloromethylketone (TLCK) and N-tosyl-L-phenylalaninyl-chloromethylketone (TPCK) do not inhibit caspase-3 and caspase-7 processing in cells exposed to pro-apoptotic inducing stimuli.
  J Cell Biochem, 105, 1501-1506.  
17993455 N.Mallorquí-Fernández, S.P.Manandhar, G.Mallorquí-Fernández, I.Usón, K.Wawrzonek, T.Kantyka, M.Solà, I.B.Thøgersen, J.J.Enghild, J.Potempa, and F.X.Gomis-Rüth (2008).
A New Autocatalytic Activation Mechanism for Cysteine Proteases Revealed by Prevotella intermedia Interpain A.
  J Biol Chem, 283, 2871-2882.
PDB codes: 3bb7 3bba
18418689 O.Riess, U.Rüb, A.Pastore, P.Bauer, and L.Schöls (2008).
SCA3: Neurological features, pathogenesis and animal models.
  Cerebellum, 7, 125-137.  
18611220 U.Bacha, J.Barrila, S.B.Gabelli, Y.Kiso, L.Mario Amzel, and E.Freire (2008).
Development of broad-spectrum halomethyl ketone inhibitors against coronavirus main protease 3CL(pro).
  Chem Biol Drug Des, 72, 34-49.
PDB code: 3d62
17167808 P.Haquette, M.Salmain, K.Svedlung, A.Martel, B.Rudolf, J.Zakrzewski, S.Cordier, T.Roisnel, C.Fosse, and G.Jaouen (2007).
Cysteine-specific, covalent anchoring of transition organometallic complexes to the protein papain from Carica papaya.
  Chembiochem, 8, 224-231.  
17935329 S.Ma, L.S.Devi-Kesavan, and J.Gao (2007).
Molecular dynamics simulations of the catalytic pathway of a cysteine protease: a combined QM/MM study of human cathepsin K.
  J Am Chem Soc, 129, 13633-13645.  
16020535 G.Nicastro, R.P.Menon, L.Masino, P.P.Knowles, N.Q.McDonald, and A.Pastore (2005).
The solution structure of the Josephin domain of ataxin-3: structural determinants for molecular recognition.
  Proc Natl Acad Sci U S A, 102, 10493-10498.
PDB code: 1yzb
16003951 S.P.Baba, S.Zehra, and B.Bano (2005).
Purification and characterization of kininogens from sheep plasma.
  Protein J, 24, 95.  
15574492 K.Wenig, L.Chatwell, U.von Pawel-Rammingen, L.Björck, R.Huber, and P.Sondermann (2004).
Structure of the streptococcal endopeptidase IdeS, a cysteine proteinase with strict specificity for IgG.
  Proc Natl Acad Sci U S A, 101, 17371-17376.
PDB code: 1y08
12554931 D.Turk, and G.Guncar (2003).
Lysosomal cysteine proteases (cathepsins): promising drug targets.
  Acta Crystallogr D Biol Crystallogr, 59, 203-213.  
12833547 L.E.Dardenne, A.S.Werneck, Oliveira Neto, and P.M.Bisch (2003).
Electrostatic properties in the catalytic site of papain: A possible regulatory mechanism for the reactivity of the ion pair.
  Proteins, 52, 236-253.  
12784208 S.Biswas, C.Chakrabarti, S.Kundu, M.V.Jagannadham, and J.K.Dattagupta (2003).
Proposed amino acid sequence and the 1.63 A X-ray crystal structure of a plant cysteine protease, ervatamin B: some insights into the structural basis of its stability and substrate specificity.
  Proteins, 51, 489-497.
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12081494 F.Lecaille, Y.Choe, W.Brandt, Z.Li, C.S.Craik, and D.Brömme (2002).
Selective inhibition of the collagenolytic activity of human cathepsin K by altering its S2 subsite specificity.
  Biochemistry, 41, 8447-8454.  
12198302 M.L.Baniecki, W.J.McGrath, Z.Dauter, and W.F.Mangel (2002).
Adenovirus proteinase: crystallization and preliminary X-ray diffraction studies to atomic resolution.
  Acta Crystallogr D Biol Crystallogr, 58, 1462-1464.  
11812789 S.Katiyar, T.Suzuki, B.J.Balgobin, and W.J.Lennarz (2002).
Site-directed mutagenesis study of yeast peptide:N-glycanase. Insight into the reaction mechanism of deglycosylation.
  J Biol Chem, 277, 12953-12959.  
12221081 T.Kashiwagi, K.Yokoyama, K.Ishikawa, K.Ono, D.Ejima, H.Matsui, and E.Suzuki (2002).
Crystal structure of microbial transglutaminase from Streptoverticillium mobaraense.
  J Biol Chem, 277, 44252-44260.
PDB code: 1iu4
11726493 D.Turk, V.Janjić, I.Stern, M.Podobnik, D.Lamba, S.W.Dahl, C.Lauritzen, J.Pedersen, V.Turk, and B.Turk (2001).
Structure of human dipeptidyl peptidase I (cathepsin C): exclusion domain added to an endopeptidase framework creates the machine for activation of granular serine proteases.
  EMBO J, 20, 6570-6582.
PDB code: 1k3b
11602025 S.Bhattacharya, S.Ghosh, S.Chakraborty, A.K.Bera, B.P.Mukhopadhayay, I.Dey, and A.Banerjee (2001).
Insight to structural subsite recognition in plant thiol protease-inhibitor complexes : understanding the basis of differential inhibition and the role of water.
  BMC Struct Biol, 1, 4.  
10691991 K.H.Choi, and R.A.Laursen (2000).
Amino-acid sequence and glycan structures of cysteine proteases with proline specificity from ginger rhizome Zingiber officinale.
  Eur J Biochem, 267, 1516-1526.  
  11206078 P.M.Smooker, J.C.Whisstock, J.A.Irving, S.Siyaguna, T.W.Spithill, and R.N.Pike (2000).
A single amino acid substitution affects substrate specificity in cysteine proteinases from Fasciola hepatica.
  Protein Sci, 9, 2567-2572.  
10806395 S.Kreusch, M.Fehn, G.Maubach, K.Nissler, W.Rommerskirch, K.Schilling, E.Weber, I.Wenz, and B.Wiederanders (2000).
An evolutionarily conserved tripartite tryptophan motif stabilizes the prodomains of cathepsin L-like cysteine proteases.
  Eur J Biochem, 267, 2965-2972.  
11042392 T.Uchikoba, K.Arima, H.Yonezawa, M.Shimada, and M.Kaneda (2000).
Amino acid sequence and some properties of phytolacain G, a cysteine protease from growing fruit of pokeweed, Phytolacca americana.
  Biochim Biophys Acta, 1523, 254-260.  
10350606 C.Czaplewski, Z.Grzonka, M.Jaskólski, F.Kasprzykowski, M.Kozak, E.Politowska, and J.Ciarkowski (1999).
Binding modes of a new epoxysuccinyl-peptide inhibitor of cysteine proteases. Where and how do cysteine proteases express their selectivity?
  Biochim Biophys Acta, 1431, 290-305.  
10410800 M.E.McGrath (1999).
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  Annu Rev Biophys Biomol Struct, 28, 181-204.  
10380356 T.Schirmeister (1999).
Inhibition of cysteine proteases by peptides containing aziridine-2,3-dicarboxylic acid building blocks.
  Biopolymers, 51, 87-97.  
  9524065 D.Turk, G.Guncar, M.Podobnik, and B.Turk (1998).
Revised definition of substrate binding sites of papain-like cysteine proteases.
  Biol Chem, 379, 137-147.  
9493267 G.Guncar, M.Podobnik, J.Pungercar, B.Strukelj, V.Turk, and D.Turk (1998).
Crystal structure of porcine cathepsin H determined at 2.1 A resolution: location of the mini-chain C-terminal carboxyl group defines cathepsin H aminopeptidase function.
  Structure, 6, 51-61.
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  9655332 M.E.McGrath, J.T.Palmer, D.Brömme, and J.R.Somoza (1998).
Crystal structure of human cathepsin S.
  Protein Sci, 7, 1294-1302.  
9125516 D.Dinakarpandian, B.Shenoy, M.Pusztai-Carey, B.A.Malcolm, and P.R.Carey (1997).
Active site properties of the 3C proteinase from hepatitis A virus (a hybrid cysteine/serine protease) probed by Raman spectroscopy.
  Biochemistry, 36, 4943-4948.  
9416427 D.H.Kim, Y.Jin, and C.H.Ryu (1997).
Inhibition of papain with 2-benzyl-3,4-epoxybutanoic acid esters. Mechanistic and stereochemical probe for cysteine protease catalysis.
  Bioorg Med Chem, 5, 2103-2108.  
  9094676 J.Ziebuhr, G.Heusipp, and S.G.Siddell (1997).
Biosynthesis, purification, and characterization of the human coronavirus 229E 3C-like proteinase.
  J Virol, 71, 3992-3997.  
9033587 M.E.McGrath, J.L.Klaus, M.G.Barnes, and D.Brömme (1997).
Crystal structure of human cathepsin K complexed with a potent inhibitor.
  Nat Struct Biol, 4, 105-109.
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9354234 N.Schaschke, I.Assfalg-Machleidt, W.Machleidt, D.Turk, and L.Moroder (1997).
E-64 analogues as inhibitors of cathepsin B. On the role of the absolute configuration of the epoxysuccinyl group.
  Bioorg Med Chem, 5, 1789-1797.  
9045680 P.R.Mittl, S.Di Marco, J.F.Krebs, X.Bai, D.S.Karanewsky, J.P.Priestle, K.J.Tomaselli, and M.G.Grütter (1997).
Structure of recombinant human CPP32 in complex with the tetrapeptide acetyl-Asp-Val-Ala-Asp fluoromethyl ketone.
  J Biol Chem, 272, 6539-6547.
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9233788 S.C.Johnston, C.N.Larsen, W.J.Cook, K.D.Wilkinson, and C.P.Hill (1997).
Crystal structure of a deubiquitinating enzyme (human UCH-L3) at 1.8 A resolution.
  EMBO J, 16, 3787-3796.
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9208091 T.S.Morris, S.Frormann, S.Shechosky, C.Lowe, M.S.Lall, V.Gauss-Müller, R.H.Purcell, S.U.Emerson, J.C.Vederas, and B.A.Malcolm (1997).
In vitro and ex vivo inhibition of hepatitis A virus 3C proteinase by a peptidyl monofluoromethyl ketone.
  Bioorg Med Chem, 5, 797-807.  
9071024 T.Shirai, and M.Go (1997).
Adaptive amino acid replacements accompanied by domain fusion in reverse transcriptase.
  J Mol Evol, 44, S155-S162.  
9158866 V.Martichonok, and J.B.Jones (1997).
Cysteine proteases such as papain are not inhibited by substrate analogue peptidyl boronic acids.
  Bioorg Med Chem, 5, 679-684.  
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The proteasome: a macromolecular assembly designed to confine proteolysis to a nanocompartment.
  Biol Chem, 378, 121-130.  
9357315 W.F.Mangel, D.L.Toledo, J.Ding, R.M.Sweet, and W.J.McGrath (1997).
Temporal and spatial control of the adenovirus proteinase by both a peptide and the viral DNA.
  Trends Biochem Sci, 22, 393-398.  
  8819168 A.J.Beveridge (1996).
A theoretical study of the active sites of papain and S195C rat trypsin: implications for the low reactivity of mutant serine proteinases.
  Protein Sci, 5, 1355-1365.  
8973203 D.Maes, J.Bouckaert, F.Poortmans, L.Wyns, and Y.Looze (1996).
Structure of chymopapain at 1.7 A resolution.
  Biochemistry, 35, 16292-16298.
PDB code: 1yal
8944787 J.Anagli, E.M.Vilei, M.Molinari, S.Calderara, and E.Carafoli (1996).
Purification of active calpain by affinity chromatography on an immobilized peptide inhibitor.
  Eur J Biochem, 241, 948-954.  
8823184 J.D.Doran, P.J.Tonge, J.S.Mort, and P.R.Carey (1996).
Deacylation and reacylation for a series of acyl cysteine proteases, including acyl groups derived from novel chromophoric substrates.
  Biochemistry, 35, 12487-12494.  
  8617222 J.Ding, W.J.McGrath, R.M.Sweet, and W.F.Mangel (1996).
Crystal structure of the human adenovirus proteinase with its 11 amino acid cofactor.
  EMBO J, 15, 1778-1783.
PDB code: 1avp
8939744 M.R.Groves, M.A.Taylor, M.Scott, N.J.Cummings, R.W.Pickersgill, and J.A.Jenkins (1996).
The prosequence of procaricain forms an alpha-helical domain that prevents access to the substrate-binding cleft.
  Structure, 4, 1193-1203.
PDB code: 1pci
8703509 T.Gonzales, and J.Robert-Baudouy (1996).
Bacterial aminopeptidases: properties and functions.
  FEMS Microbiol Rev, 18, 319-344.  
8605158 Y.Chen, Y.T.Ma, and R.R.Rando (1996).
Solubilization, partial purification, and affinity labeling of the membrane-bound isoprenylated protein endoprotease.
  Biochemistry, 35, 3227-3237.  
  8520469 B.A.Malcolm (1995).
The picornaviral 3C proteinases: cysteine nucleophiles in serine proteinase folds.
  Protein Sci, 4, 1439-1445.  
7622473 T.Vernet, D.C.Tessier, J.Chatellier, C.Plouffe, T.S.Lee, D.Y.Thomas, A.C.Storer, and R.Ménard (1995).
Structural and functional roles of asparagine 175 in the cysteine protease papain.
  J Biol Chem, 270, 16645-16652.  
7890671 Z.Jia, S.Hasnain, T.Hirama, X.Lee, J.S.Mort, R.To, and C.P.Huber (1995).
Crystal structures of recombinant rat cathepsin B and a cathepsin B-inhibitor complex. Implications for structure-based inhibitor design.
  J Biol Chem, 270, 5527-5533.
PDB codes: 1cpj 1cte 1the
  7920263 L.C.Pedersen, V.C.Yee, P.D.Bishop, I.Le Trong, D.C.Teller, and R.E.Stenkamp (1994).
Transglutaminase factor XIII uses proteinase-like catalytic triad to crosslink macromolecules.
  Protein Sci, 3, 1131-1135.  
9383368 Z.Li, X.Chen, E.Davidson, O.Zwang, C.Mendis, C.S.Ring, W.R.Roush, G.Fegley, R.Li, and P.J.Rosenthal (1994).
Anti-malarial drug development using models of enzyme structure.
  Chem Biol, 1, 31-37.  
1541261 W.Bode, and R.Huber (1992).
Natural protein proteinase inhibitors and their interaction with proteinases.
  Eur J Biochem, 204, 433-451.  
  1868826 D.Musil, D.Zucic, D.Turk, R.A.Engh, I.Mayr, R.Huber, T.Popovic, V.Turk, T.Towatari, and N.Katunuma (1991).
The refined 2.15 A X-ray crystal structure of human liver cathepsin B: the structural basis for its specificity.
  EMBO J, 10, 2321-2330.
PDB code: 1huc
2326252 P.C.Moews, J.R.Knox, O.Dideberg, P.Charlier, and J.M.Frère (1990).
Beta-lactamase of Bacillus licheniformis 749/C at 2 A resolution.
  Proteins, 7, 156-171.
PDB code: 2blm
  2303031 R.Felleisen, and M.Q.Klinkert (1990).
In vitro translation and processing of cathepsin B of Schistosoma mansoni.
  EMBO J, 9, 371-377.  
2920736 J.M.Van der Laan, M.B.Swarte, H.Groendijk, W.G.Hol, and J.Drenth (1989).
The influence of purification and protein heterogeneity on the crystallization of p-hydroxybenzoate hydroxylase.
  Eur J Biochem, 179, 715-724.  
  3067861 B.D.Korant (1988).
Viral proteases: an emerging therapeutic target.
  Crit Rev Biotechnol, 8, 149-157.  
3285343 J.C.Carrington, and W.G.Dougherty (1988).
A viral cleavage site cassette: identification of amino acid sequences required for tobacco etch virus polyprotein processing.
  Proc Natl Acad Sci U S A, 85, 3391-3395.  
  3191914 W.Bode, R.Engh, D.Musil, U.Thiele, R.Huber, A.Karshikov, J.Brzin, J.Kos, and V.Turk (1988).
The 2.0 A X-ray crystal structure of chicken egg white cystatin and its possible mode of interaction with cysteine proteinases.
  EMBO J, 7, 2593-2599.
PDB code: 1cew
3475008 E.T.Kaiser (1987).
Preparation of flavopapain and other semisynthetic enzymes.
  Ann N Y Acad Sci, 501, 14-20.  
  6518326 A.H.Louie, and R.L.Somorjai (1984).
Stieltjes integration and differential geometry: a model for enzyme recognition, discrimination, and catalysis.
  Bull Math Biol, 46, 745-764.  
6928689 J.B.Henes, M.S.Briggs, S.G.Sligar, and J.S.Fruton (1980).
Fluorescence energy transfer studies on the active site of papain.
  Proc Natl Acad Sci U S A, 77, 940-943.  
36609 A.L.Fink, and P.Meehan (1979).
Detection and accumulation of tetrahedral intermediates in elastase catalysis.
  Proc Natl Acad Sci U S A, 76, 1566-1569.  
488108 L.Polgár (1979).
Deuterium isotope effects on papain acylation. Evidence for lack of general base catalysis and for enzyme--leaving-group interaction.
  Eur J Biochem, 98, 369-374.  
28228 K.G.Allen, J.A.Stewart, P.E.Johnson, and D.G.Wettlaufer (1978).
Identification of the functional ionic groups of papain by pH/rate profile analysis.
  Eur J Biochem, 87, 575-582.  
689035 L.Polgár, and P.Halász (1978).
Evidence for multiple reactive forms of papain.
  Eur J Biochem, 88, 513-521.  
661956 W.G.Hol, P.T.van Duijnen, and H.J.Berendsen (1978).
The alpha-helix dipole and the properties of proteins.
  Nature, 273, 443-446.  
913417 M.R.Bendall, I.L.Cartwright, P.I.Clark, G.Lowe, and D.Nurse (1977).
Inhibition of papain by N-acyl-aminoacetaldehydes and N-acyl-aminopropanones. Evidence for hemithioacetal formation by a cross-saturation technique in nuclear-magnetic resonance spectroscopy.
  Eur J Biochem, 79, 201-209.  
923564 P.Halász, and L.Polgár (1977).
Negatively charged reactants as probes in the study of the essential mercaptide-imidazolium ion-pair of thiolenzymes.
  Eur J Biochem, 79, 491-494.  
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