Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.22.6 (chymopapain)
 407 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cysteine proteinase inhibitor cystatin, from chicken egg white, bound with equimolar stoichiometry to the cysteine proteinases actinidin, chymopapain A, and ficin. The changes of near-ultraviolet absorption and fluorescence induced by the binding differed appreciably for the three enzymes, indicating that these spectral changes arise predominantly from aromatic residues in the proteinases. In contrast, the near-ultraviolet circular dichroism changes were similar for all three enzymes, supporting previous evidence that these changes originate mainly from the single tryptophan residue in cystatin, Trp-104. The pseudo-first-order rate constant for the binding increased linearly with the inhibitor concentration up to as high concentrations as could be measured for the three proteinases. This behavior is consistent with the complexes being formed by simple, bimolecular reactions, as was concluded previously for the reaction of cystatin with active and inactivated forms of papain. The second-order association rate constant varied only about 4-fold, from 2.2 X 10(6) to 9.6 X 10(6) M-1.s-1, for the three enzymes, the higher of these values being similar to that measured previously for the reaction with papain. These observations are consistent with the association rate being governed mainly by the frequency of collision between the binding areas of enzyme and inhibitor. All three cystatin-proteinase complexes dissociated to intact inhibitor, demonstrating reversibility. The dissociation rate constants varied about 20000-fold, from 4.6 X 10(-7) s-1 for ficin to 1.1 X 10(-2) s-1 for actinidin, reflecting substantial differences between the enzymes in the nature of the interactions with the inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Interaction between chicken cystatin and the cysteine proteinases actinidin, chymopapain A, and ficin. 233 64

Chymopapain A was isolated from the dried latex of papaya (Carica papaya) by ion-exchange chromatography followed by covalent chromatography by thiol-disulphide interchange. The latter procedure was used to produce fully active enzyme containing one essential thiol group per molecule of protein, to establish that the chymopapain A molecule contains, in addition, one non-essential thiol group per molecule and to recalculate the literature value of epsilon 280 for the enzyme as 36 000 M-1 X cm -1. The Michaelis parameters for the hydrolysis of L-benzoylarginine p-nitroanilide and of benzyloxy-carbonyl-lysine nitrophenyl ester at 25 degrees C, and I 0.1 at several pH values catalysed by chymopapain A, papaya proteinase omega, papain (EC 3.4.22.2) and actinidin (EC 3.4.22.14) were determined. Towards these substrates chymopapain A has kcat./km values similar to those of actinidin and of papaya proteinase omega and significantly lower than those of papain or ficin. The environment of the catalytic site of chymopapain A is markedly different from those of other cysteine proteinases studied to date, as evidenced by the pH-dependence of the second-order rate constant (k) for the reaction of the catalytic-site thiol group with 2,2'-dipyridyl disulphide. The striking bell-shaped component that is a characteristic feature of the reactions of S-/ImH+ (thiolate/imidazolium) ion-pair components of many cysteine-proteinase catalytic sites with the 2,2'-dipyridyl disulphide univalent cation is not present in the pH-k profile for the chymopapain A reaction. The result is consistent with the presence of an additional positive charge in, or near, the catalytic site that repels the cationic form of the probe reagent. Resonance Raman spectra were collected at pH values 2.5, 6.0 and 8.0 for each of the following dithioacyl derivatives of chymopapain A: N-benzoylglycine-, N-(Beta-phenylpropionl)glycine- and N-methoxycarbonylphenylalanylglycine-. The main conclusion of the spectral study is that in each case the acyl group binds as a single population known as conformer B in which the glycinic N atom is in close contact with the thiol S atom of the catalytic-site cysteine residue, as is the case also for papain and other cysteine proteinases studied. Thus the abnormal catalytic-site environment of chymopapain A detected by the reactivity-probe studies, which may have consequences for the acylation step of the catalytic act, does not perturb the conformation of the bound acyl group at the acyl-enzyme-intermediate stage of catalysis.
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PMID:Chymopapain A. Purification and investigation by covalent chromatography and characterization by two-protonic-state reactivity-probe kinetics, steady-state kinetics and resonance Raman spectroscopy of some dithioacyl derivatives. 351 53

1. 2-(N'-Acetyl-L-phenylalanylamino)ethyl 2'-pyridyl disulphide [compound (III)] and 2-(acetamido)ethyl 2'-pyridyl disulphide [compound (IV)] were synthesized by acylation of the common intermediate, 2-aminoethyl 2'-pyridyl disulphide, to provide examples of chromogenic thiol-specific substrate-derived two-protonic-state electrophilic probe reagents. These two reagents, together with n-propyl 2-pyridyl disulphide [compound (II)], provide structural variation in the non-pyridyl part of the molecule from a simple hydrocarbon side chain in compound (II) to a P1-P2 amide bond in compound (IV) and further to both a P1-P2 amide bond and a hydrophobic side chain (of phenylalanine) at P2 as a potential occupant of S2 subsites. 2. These disulphides were used as reactivity probes to investigate specificity and binding-site-catalytic-site signalling in a number of cysteine proteinases by determining (a) the reactivity at pH 6.0 at 25 degrees C at I 0.1 of compound (III) (a close analogue of a good papain substrate) towards 2-mercaptoethanol, benzimidazol-2-ylmethanethiol [compound (V), as a minimal catalytic-site model], chymopapains B1-B3, chymopapain A, papaya proteinase omega, actinidin, cathepsin B and papain, (b) the effect of changing the structure of the probe as indicated above on the reactivities of compound (V) and of the last five of these enzymes, and (c) the forms of pH-dependence of the reactivities of papain and actinidin towards compound (III). 3. The kinetic data suggest that reagents of the type investigated may be sensitive probes of molecular recognition features in this family of enzymes and are capable not only of detecting differences in binding ability of the various enzymes but also of identifying enzyme-ligand contacts that provide for binding-site-catalytic-site signalling mechanisms. 4. The particular value of this class of probe appears to derive from the possibility of activating the 2-mercaptopyridine leaving group not only by formal protonation, as was recognized previously [see Brocklehurst (1982) Methods Enzymol. 87C, 427-469], but also by hydrogen-bonding to the pyridyl nitrogen atom when the appropriate geometry in the catalytic site is provided by enzyme-ligand contacts involving the non-pyridyl part of the molecule.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Substrate-derived two-protonic-state electrophiles as sensitive kinetic specificity probes for cysteine proteinases. Activation of 2-pyridyl disulphides by hydrogen-bonding. 366 11

Cysteine proteinases are widely distributed among living organisms. According to the most recent classifications (Rawlings and Barrett, 1993, 1994), they can be subdivided on the basis of sequence homology into 14 or even 20 different families, the most important being the papain and the calpain families. The papain-like cysteine proteinases are the most abundant among the cysteine proteinases. The family consists of papain and related plant proteinases such as chymopapain, caricain, bromelain, actinidin, ficin, and aleurain, and the lysosomal cathepsins B, H, L, S, C and K. Most of these enzymes are relatively small proteins with Mr values in the range 20000-35000 (reviewed in Brocklehurst et al., 1987; Polgar, 1989; Rawlings and Barrett, 1994; Berti and Storer, 1995), with the exception of cathepsin C, which is an oligomeric enzyme with Mr approximately 200000 (Metrione et al., 1970; Dolenc et al., 1995). A number of cysteine proteinases are located within lysosomes. Four of them, cathepsins B, C, H and L, are ubiquitous in lysosomes of animals, whereas cathepsin S has a more restricted localisation (Barrett and Kirschke, 1981; Kirschke and Wiederanders, 1994). The enzymes, except cathepsin C, are endopeptidases (reviewed in Kirschke et al., 1995), although cathepsin B was found also to be a dipeptidyl carboxypeptidase (Aronson and Barrett, 1978) and cathepsin H also an aminopeptidase (Koga et al., 1992). Cathepsin C is a dipeptidyl aminopeptidase, but at higher pH it exhibits also dipeptidyl transferase activity (reviewed in Kirschke et al., 1995). Among the lysosomal cysteine proteinases, cathepsin L was found to be the most active in degradation of protein substrates, such as collagen, elastin and azocasein (Barrett and Kirschke, 1981; Maciewicz et al., 1987; Mason et al., 1989), arid cathepsin B the most abundant (Kirschke and Barrett, 1981). All the enzymes are optimally active at slightly acidic pH, although their pH optima for degradation of synthetic substrates vary from 5.5 for cathepsin L to 6.8 for cathepsin H (reviewed in Kirschke et al., 1995). Several other lysosomal cysteine proteinases, such as cathepsins N, T and K, are known, although their properties are less well characterised (reviewed in Kirschke et al., 1995). In particular cathepsin K has attracted recent interest (Bromme et al., 1996; Shi et al., 1995; Bossard et al., 1996; Drake et al., 1996) and was found to be expressed specifically in osteoclasts (Drake et al., 1996) with properties similar to cathepsin L (Bossard et al., 1996).
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PMID:Structural and functional aspects of papain-like cysteine proteinases and their protein inhibitors. 916 64

The amino acid sequences of ananain (EC3.4.22.31) and stem bromelain (3.4.22.32), two cysteine proteases from pineapple stem, are similar yet ananain and stem bromelain possess distinct specificities towards synthetic peptide substrates and different reactivities towards the cysteine protease inhibitors E-64 and chicken egg white cystatin. We present here the complete amino acid sequence of ananain and compare it with the reported sequences of pineapple stem bromelain, papain and chymopapain from papaya and actinidin from kiwifruit. Ananain is comprised of 216 residues with a theoretical mass of 23464 Da. This primary structure includes a sequence insert between residues 170 and 174 not present in stem bromelain or papain and a hydrophobic series of amino acids adjacent to His-157. It is possible that these sequence differences contribute to the different substrate and inhibitor specificities exhibited by ananain and stem bromelain.
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PMID:Complete amino acid sequence of ananain and a comparison with stem bromelain and other plant cysteine proteases. 935 53

Kiwifruit cysteine proteinase inhibitors (KCPIs) were purified from the cortex and seeds of kiwifruit after inactivation of the abundant cortex cysteine proteinase actinidain. One major (KCPI1) and four minor cystatins were identified from Actinidia deliciosa ripe mature kiwifruit cortex as well as a seed KCPI from A. chinensis. The predominant cortex cystatin, KCPI1, inhibited clan CA, family C1 (papain family) cysteine proteinases (papain, chymopapain, bromelain, ficin, human cathepsins B, H and L, actinidain and the house dust mite endopeptidase 1), while cysteine proteinases belonging to other families, [clostripain (C11), streptopain (C10) and calpain (C2)] were not inhibited. Inhibition constants (K(I)) ranged between 0.001 nM for cathepsin L and 0.98 nM for endopeptidase 1. The K(I) (14 nM) for KCPI1 inhibiting actinidain is at least 2 orders of magnitude higher than for other plant proteinases measured. The cortex KCPI1 and a seed KCPI purified from seeds had the same N-terminal sequence (VAAGGWRPIESLNSAEVQDV). BLAST-matching the peptide sequence against an in-house generated Actinidia EST database, identified 81 cDNAs that exactly matched the measured KCPI1 peptide sequence. Peptide sequences of two other cortex KCPIs each exactly matched a predicted peptide sequence of a cDNA from kiwifruit. The predicted peptide sequence of KCPI1 of 116 amino acids encodes a signal peptide and does not contain cysteine. Without the signal peptide (mature protein), KCPI1 has a molecular mass of approximately 11 kDa, possesses the consensus sequence characteristic for the phytocystatins and shows the highest homology to a cystatin from Citrusxparadisi (52% identity). This is the first report of phytocystatins from the Ericales.
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PMID:Purification and characterization of phytocystatins from kiwifruit cortex and seeds. 1469 68