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Papain is a plant proteolytic enzyme for the cysteine proteinase family cysteine protease enzyme in which enormous progress has been made to understand its functions. Papain is found naturally in papaya (Carica papaya L.) manufactured from the latex of raw papaya fruits. The enzyme is able to break down organic molecules made of amino acids, known as polypeptides and thus plays a crucial role in diverse biological processes in physiological and pathological states, drug designs, industrial uses such as meat tenderizers and pharmaceutical preparations. The unique structure of papain gives it the functionality that helps elucidate how proteolytic enzymes work and also makes it valuable for a variety of purposes. In the present review, its biological importance, properties and structural features that are important to an understanding of their biological function are presented. Its potential for production and market opportunities are also discussed.
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American Journal of Biochemistry and Biotechnology, 2012, 8 (2), 99-104
ISSN: 1553-3468
© 2012 Amri and Mamboya, This open access article is distributed under a Creative Commons Attribution
(CC-BY) 3.0 license
doi:10.3844/ajbbsp.2012.99.104 Published Online 8 (2) 2012 (http://www.thescipub.com/ajbb.toc)
99
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PAPAIN, A PLANT ENZYME OF BIOLOGICAL IMPORTANCE:
A REVIEW
Ezekiel Amri
and Florence Mamboya
Department of Science and Laboratory Technology,
Dar es Salaam Institute of Technology (DIT), P. O. Box 2958, Dar es Salaam, Tanzania
Received 2012-05-13; Revised 2012-05-20; Accepted 2012-06-02
ABSTRACT
Papain is a plant proteolytic enzyme for the cysteine proteinase family cysteine protease enzyme in which
enormous progress has been made to understand its functions. Papain is found naturally in papaya (Carica
papaya L.) manufactured from the latex of raw papaya fruits. The enzyme is able to break down organic
molecules made of amino acids, known as polypeptides and thus plays a crucial role in diverse biological
processes in physiological and pathological states, drug designs, industrial uses such as meat tenderizers and
pharmaceutical preparations. The unique structure of papain gives it the functionality that helps elucidate
how proteolytic enzymes work and also makes it valuable for a variety of purposes. In the present review,
its biological importance, properties and structural features that are important to an understanding of their
biological function are presented. Its potential for production and market opportunities are also discussed.
Keywords: Proteolytic enzyme, cysteine protease, papain, structure, hydrophobic
1. INTRODUCTION
Papain (EC 3.4.22.2) is an endolytic plant cysteine
protease enzyme which is isolated from papaya (Carica
papaya L.) latex. Papain is obtained by cutting the skin
of the unripe papaya and then collecting and drying the
latex which flows from the cut. The greener the fruit,
more active is the papain. Papain enzyme belongs to the
papain superfamily, as a proteolytic enzyme, papain is of
crucial importance in many vital biological processes in
all living organisms (Tsuge et al., 1999). Papain shows
extensive proteolytic activity towards proteins, short-
chain peptides, amino acid esters and amide links and is
applied extensively in the fields of food and medicine
(Uhlig, 1998). It preferentially cleaves peptide bonds
involving basic amino acids, particularly arginine, lysine
and residues following phenylalanine (Menard et al.,
1990). The unique structure of papain gives its
functionality that helps to understand how this
proteolytic enzyme works and it’s useful for a variety
of purposes. This review addresses structural features
of enzyme, the biological importance and processes in
which papain participates and its potential for
production market opportunities.
1.1. Properties, Structure and Features of Papain
The globular protein, the papain PDB accession
number 1CVZ is a single chain protein with molecular
weight of 23,406 DA and consists of 212 amino acid
with four disulfide bridges and catalytically important
residues in the following positions Gln19, Cys25, His158
and His159 (Mitchel et al., 1970; Robert et al., 1974;
Tsuge et al., 1999). The graphical representation of the
amino acid composition of papain is shown in Fig. 1.
Papain is a cysteine hydrolase that is stable and active
under a wide range of conditions. It is very stable even at
elevated temperatures (Cohen et al., 1986). Papain is
unusually defiant to high concentrations of denaturing
agents, such as, 8M urea or organic solvent like 70%
EtOH. Optimum pH for activity of papain is in the
range of 3.0-9.0 which varies with different substrate
(Edwin and Jagannadham, 2000; Ghosh, 2005).
Papain enzyme as cysteine proteases in papain
superfamily is usually consisting of two well-defined
domains which provide an excellent system for studies
in understanding the folding-unfolding behavior of
proteins (Edwin et al., 2002).
Ezekiel Amri and Florence Mamboya / American Journal of Biochemistry and Biotechnology 8 (2) (2012) 99-104
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Fig. 1. Graphical representation of the amino acid composition of papain
Fig. 2. Papain structure (MMDB protein structure summary,
1CVZ)
Fig. 3. Hydrophobic amino acid of papain (1CVZ). Colored gray
in a space fill model are the
backbone oxygen and nitrogen
of the residues with the hydrophobic side chain (Source:
http://www.oocities.org/bramsugar/intro4.html).
The protein is stabilized by three disulfide bridges in
which the molecule is folded along these bridges
creating a strong interaction among the side chains
which contributes to the stability of the enzyme (Edwin
and Jagannadham, 2000; Tsuge et al., 1999). Its
three-dimensional structure consists of two distinct
structural domains with a cleft between them. This cleft
contains the active site, which contains a catalytic diad
that has been likened to the catalytic triad of
chymotrypsin. The catalytic diad is made up of the
amino acids-cysteine-25 (from which it gets its
classification) and histidine-159. Aspartate-158 was
thought to play a role analogous to the role of aspartate
in the serine protease catalytic triad, but that has since
then been disproved (Menard et al., 1990).
Papain molecule has an all-α domain and an
antparallel β-sheet domain (Kamphuis et al., 1984;
Madej et al., 2012). The conformational behavior of
papain in aqueous solution has been investigated in the
presence of SDS and reported to show high α-helical
content and unfolded structure of papain in the presence of
SDS is due to strong electrostatic repulsion (Huet et al.,
2006). In the molten globule state (pH 2.0), papain show
evidence of substantial secondary structure as ß-sheet
and is relatively less denatured compared to 6 M
Guanidium Hydroc8hloride (GnHCl), the enzyme also
exhibits a great tendency to aggregate at lower
concentrations of GnHCl or a high concentration of salt
(Edwin and Jagannadham, 2000). Papain apart from
being most studied plant cysteine proteases, further
researches in understanding the specificity, the structural
the effect brought by inhibitors, low pH, metal ions and
fluorinated alcohols has been identified as of critical
importance (Huet et al., 2006; Naeem et al., 2006).
Figure 2 shows the structure of papain from Molecular
Modeling Database (MMDB), the structure is shown
with all-α domain and an antparallel ß-sheet domain.
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1.2. Hydrophobicity of Papain
It is often useful to examine the relative
hydrophobicity or hydrophilicity values of the amino
acids in a protein sequence. Since hydrophobic residues
tend to be more buried in the interior of the molecule and
hydrophilic residues are more exposed to solvent, a
profile of these values can indicate the overall folding
pattern. The hydrophobic interactions have the major
influence in protein conformation and the most
hydrophobic of the amino acid side chains are those of
alanine, Valine, leucine, methionine and Isoleucine
which vary in degrees of hydrophobic. The hydrophobic
-hydrophilic interaction of papain amino acids in the side
chain seems to be the major thermodynamic forces
which drive protein folding. Investigation of the
formation of the intermediate state of papain through
inducing n-alkyl sulfates including sodium octyl sulfate,
SOS; sodium decyl sulfate, SDeS; and sodium dodecyl
sulfate, SDS at different concentrations has exhibited
that hydrophobic interactions play an important role in
inducing the two different intermediates along the two
various thermodynamic pathways (Chamani et al.,
2009). Catalytic activity of papain involves hydrolysis of
proteins with broad specificity for peptide bonds, but
preference for an amino acid bearing a large hydrophobic
side chain at the P2 position while does not accept Val in
P1 (Kamphuis et al., 1985). The enzyme has been
reported to be generally more stable in hydrophobic
solvents and at lower water contents and can catalyze
reactions under a variety of conditions in organic
solvents with its substrate specificity little changed from
that in aqueous media (Stevenson and Storer, 1991). In
general, native proteins have a hydrophobic core and a
charged and/or polar group on the surface. The
hydrophobic core helps to stabilize the tertiary structure of
the protein by hydrophobic interaction
while the outer
polar surfaces preferentially interact with the exterior
aqueous medium (Wang et al., 2006). Figure 3 shows
hydrophobic amino acid of papain in space fill model.
Hyrophobicity of papain using carbon distribution
profile along the sequence of papain is shown in Fig. 4.
The graph indicates that carbon content is maintained at
31.45% of carbon all along the sequence. Some regions
along the sequences have values above 31.45%, these are
considered to be higher hydrophobic regions as it has
previously been reported when using carbon content
distribution profile (Rajasekaran and Vijayasarathy, 2011).
Thus, the overall hydrophobicity of papain enzyme being
maintained at 31.45% of carbon all along the sequence
contribute to stability of protein as previous been reported
that stable and ordered proteins maintain 31.45% of
carbon all along the sequence (Jayaraj et al., 2009).
1.3. Mechanism, Biological Importance and
Functions
1.4. Mechanism of Functions
The mechanism in which the function of papain is
made possible is through the cysteine-25 portion of the
triad in the active site that attacks the carbonyl carbon in
the backbone of the peptide chain freeing the amino
terminal portion. As this occurs throughout the peptide
chains of the protein, the protein breaks apart. The
mechanism by which it breaks peptide bonds involves
deprotonation of Cys-25 by His-159. Asparagine-175
helps to orient the imidazole ring of His-159 to allow
this deprotonation to take place. Although far apart
within the chain, these three amino acids are in close
proximity due to the folding structure. It is though these
three amino acids working together in the active site that
provides this enzyme with its unique functions. Cys-25
then performs a nucleophilic attack on the carbonyl
carbon of a peptide backbone (Menard et al., 1990;
Tsuge et al., 1999). In the active site of papain, Cys -25
and His -159 are thought to be catalytically active as a
thiolate-imidazolium ion pair. Papain can be efficiently
inhibited by peptidyl or non-peptidyl N-nitrosoanilines
(Guo et al., 1996; 1998). The inactivation is due to the
formation of a stable S-NO bond in the active site (S-
nitroso-Cys
25
) of papain (Xian et al., 2000).
1.5. Papain in Medical Uses
Papain acts as a debris-removing agent, with no
harmful effect on sound tissues because of the enzyme’s
specificity, acting only on the tissues, which lack the α1-
antitripsine plasmatic antiprotease that inhibits proteolysis
in healthy tissues (Flindt, 1979). The mechanism of
biochemical removal of caries involves cleavage of
polypeptide chains and/or hydrolysis of collagen cross-
linkages. These cross-linkages give stability to the
collagen fibrils, which become weaker and thus more
prone to be removed when exposed to the papain gel
(Beeley et al., 2000). Papain-based gel has also been
reported as a potential useful in biochemical
excavation procedures for dentin (Piva et al., 2008).
Papain has advantages for being used for
chemomechanical dental caries removal since it does
not interfere in the bond strength of restorative
materials to dentin (Lopes et al., 2007).
Papain enzyme has a long history of being used to
treat sports injuries, other causes of trauma and allergies
(Dietrich, 1965). Fortunately papain has a proven track
record in managing all of these conditions with clinical
evidence of significant benefits for use of papain
protease enzyme in cases of sports injury.
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Fig. 4. Carbon distribution profile along the sequence of papain (1CVZ)
It has previously been reported that minor injuries healed
faster with papain proteases than with placebos.
Furthermore, athletes using papain protease supplements
were able to cut recovery time from 8.4 days to 3.9 days
(Trickett, 1964; Dietrich, 1965). Papain also has been
successfully used to overcome the allergies associated
with leaky gut syndrome, hypochlorhydria (insufficient
stomach acid) and intestinal symbiosis like gluten
intolerance. Papain has previously been reported to have
significant analgesic and anti-inflammatory activity against
symptoms of acute allergic sinusitis like headache and
toothache pain without side effects (Mansfield et al., 1985).
1.6. Papain Uses in Drug Design
Papain shares many features with physiologically
important mammalian cysteine proteases and show nearly
identical folding patterns especially around the active site
which has been useful for drug design (Meara and Rich,
1996). The X-ray coordinate system for papain solved at 1.7
A resolutions is a representative example of the structure of
a covalent ligand-bound cysteine protease complex
particularly in the papain superfamily (Tsuge et al., 1999).
Thus, papain is reported to be useful as an experimental
model structure to understand the inhibition mechanism of
newly developed specific inhibitors of cathepsin L, the
papain superfamily and its an antioxidant properties can be
useful in preventing certain types of illnesses (Tsuge et al.,
1999; Gayosso-Garcia et al., 2010). Since most of the
amino acid residues that are involved in the binding to
papain are conserved in cathepsin L, this publicly available
high resolution structure has provided an excellent model
for the successful design of highly active and specific
cathepsin L inhibitors (Katunuma et al., 1999). Papain is
also reported to be used as a surrogate enzyme in a drug
design effort to obtain potent and selective inhibitors of
cathepsin K, a new member of the papain superfamily of
cysteine proteases that is selected and highly expressed
in osteoclasts (LaLonde et al., 1998). Papain is also
reported to be useful as catalyzed (co) oligomerization of
α-amino acids (Schwab et al., 2012).
1.7. Industrial Uses and Pharmaceutical
Preparations
Papain is used in meat tenderizers; the major meat
proteins responsible for tenderness are the myofibrillar
proteins and the connective tissue proteins. Protease
enzymes are used to modify these proteins and papain has
been extensively used as a common ingredient in the
brewery and in the meat and meat processing (Khanna and
Panda, 2007). Papain importance as tenderizers in the food
industry is similar to collagenases, which have application
in the fur and hide tanning to ensure uniform dying of
leather. Papain also can act as a clarifying agent in many
food industry processes. As a protein digestant, papain is
used in combating dyspepsia and other digestive disorders
and disturbances of the gastrointestinal tract (Huet et al.,
2006). Papain has for quite a long time been used in
pharmaceutical preparations of diverse food manufacturing
applications as the production of high quality kunafa and
other popular local sweets and pastries. Papain has been
reported to improve meltability and stretchability of Nabulsi
cheese with outstanding fibrous structure enhancing
superiority in the application in kunafa, pizza and pastries
(Abu-Alruz et al., 2009). Also as pharmaceutical products
in gel based a proteolytic cisteine enzyme, papain presents
antifungal, antibacterial and anti-inflammatory properties
(Chukwuemeka and Anthoni, 2010).
1.8. Potential for Production and Market
Opportunities
Papain enzyme is extracted from Carica papaya
which is a tropical and a herbaceous succulent plant that
possess self supporting stems which grows in all tropical
countries and many sub-tropical regions of the world
(Jaime et al., 2007). Moreover, there is no limitation due
to seasonality as the papaya is available almost round the
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year. Consequently, there is a need to facilitate the
entrepreneurs in understanding the potential of papaya
production and the importance of setting up a unit of
papain. A well managed papaya production has recorded
higher papain yield of 8.17 g per fruit and highest papain
of 686.29 g per plant in a period of 6 months
(Kamalkumar et al., 2007; Reddy et al., 2012). Papain is
used in many industries such as breweries,
pharmaceuticals, food, leather, detergents, meat and
fish processing for a variety of processes. Therefore,
the end use segments are many in signifying that
papain has high export demand. Since there are good
prospects for papain market, the papaya production
and extraction of papain can be a high source of
income even for small farmers.
2. CONCLUSION
Papain has revealed to be an enzymatic protein of
significant biological and economic importance. It is
through the unique structure of papain that provides
functionality and helps explain how this proteolytic
enzyme works and also makes it valuable for a variety of
purposes. Further researches on papain enzyme in
understand the specificity, the structural the effect
brought various thermodynamic pathways is of critical
importance. Papain is found naturally in papaya which is
a versatile plant having number of uses and enzymatic
properties. Since the papaya grows in a wide range of
climate, papaya production for extraction of papain can
be a source of earning a high income to farmers.
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... Papain is a plant protease isolated from unripe papaya latex (Carica papaya L.). Papain shows good proteolytic activity and can be applied in VCO production (Amri and Mamboya, 2012). Mansor et al. (2012), found that addition of 0.1% (w/w) papain produce VCO with 46.36% lauric acid. ...
... The ϑirst is pepsin-like aspartic proteases produced by N. sitophila, which tend to cleave dipeptide bonds that have hydrophobic residues (Mahajan and Badgujar, 2010). Next, L. Plantarum produces trypsin-like serine protease, which cleaves peptides on the carboxyl side of the amino acids lysine or arginine, which is arginine or lysine (Amri and Mamboya, 2012). The analysis result of crude papain proteolytic activity was 117.87 U/mL. ...
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... The efficiency of papain mechanism of action is dictated by the cysteine-25 component of the triad located at the active side when the pH of the enzyme is in the optimum range ranging from 3.0 to 9.0 and the temperature of 60 to 70 • C (Amri & Mamboya, 2012). The presence of asparagine-175 bonded with histidine-159 increases papain catalytic action by attracting the carbonyl carbon in the backbone of the peptide chain, causing the bond to break and the amino group terminal part to be released. ...
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... Previous studies showed that papain inclusion in aquafeed promotes growth performance and improved feed utilisation in sterlet (Acipencer ruthenus; Wiszniewski et al., 2022), African catfish (Clarias gariepinus; Rachmawati et al., 2019), mahseer (Tor tambra; Muchlisin et al. 2016) and rohu (Labeo rohita; Khati et al., 2015). Papain is predominantly the plant's latex, but the enzyme is also detected in every part of the plant (Mamboya and Amri, 2012;Nwinyi and Abikoye, 2010). Papaya leaf is often regarded as agricultural waste. ...
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... The catalytic activity of papain is provided by the amino acid residues Cys 25 and His 159 . An important role is played by Asn 175 , the interaction of which with imidazole ring of His 159 provides the correct tertiary structure of the protein necessary for the deprotonation of the catalytic domain of Cys 25 [17]. For the first time papain was isolated in 1879 from latex [12]. ...
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Problem statement: Boiled white brined cheese (Nabulsi cheese) is the mostly consumed cheese in Jordan; this cheese should show meltability and high stretchability in order to fit in the production of high quality Kunafa and other popular local sweets and pastries. However, these characteristics are rarely available when usual processing and preservation methods were used. Approach: This study was based on the hypothesis that it would be possible to imply meltability and stretchability to the cheese by proteolytic enzymes to the original brine that may specifically act on cross linking bonds of casein. In this study, six commercial proteases were used. Results: It was found that Nabulsi cheese treated with papain developed an outstanding fibrous structure, this gives superiority in the application in kunafa, pizza and pastries. The meltability and stretchability of Nabulsi cheese treated with papain were still excellent after 4 weeks of storage; this indicated the restricted enzyme action, probably due to high salt concentrations (18%) in storage brine. Conclusion: Use of proteolytic enzymes to induce meltability and stretchability of Nabulsi cheese was proved to be an efficient method.
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Papaya (Carica papaya L.) is a popular and economically important fruit tree of tropical and subtropical countries. The fruit is consumed world-wide as fresh fruit and as a vegetable or used as processed products. This review focuses primarily on two aspects. Firstly, on advances in in vitro methods of propagation, including tissue culture and micropropagation, and secondly on how these advances have facilitated improvements in papaya genetic transformation. An account of the dietary and nutritional composition of papaya, how these vary with culture methods, and secondary metabolites, both beneficial and harmful, and those having medicinal applications, are discussed. An overview of papaya post-harvest is provided, while ‘synseed’ technology and cryopreservation are also covered. This is the first comprehensive review on papaya that attempts to integrate so many aspects of this economically and culturally important fruit tree that should prove valuable for professionals involved in both research and commerce.
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Increasingly, public debate on ban of use of synthetic chemicals for pest control has been unabated, due basically to the hazards posed by such chemicals to the ecosystem and environment. Biological control using natural products presents as alternative and a viable means of control of pests. Effects of extracts from Carica papaya. L (seed and papain) on mycelial reduction of the most occurring fungal pathogen causing pawpaw fruit rot were investigated. Different fungi isolated were Rhizopus spp, Aspergillus spp and Mucor spp. The aqueous seed extract and papain exhibited remarkable mycelial inhibition with mean zones of inhibitions between (0.23 - 1.73 mm). Using ANOVA at 5% (P < 0.05) there seem to be no significant difference in activity between the extracts (aqueous seed extract and papain).The importance of these findings is hinged on non-chemical means of shelf life elongation of harvested pawpaw fruit in Africa.
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Four hydrophobic amino acids (Leu, Tyr, Phe, Trp) were oligomerized by the protease papain in homo-oligomerization, binary co-oligomerization and ternary co-oligomerization. After 24 h, solid polydisperse reaction products of the homo-oligomerization were obtained in yields ranging from 30-80% by weight. A DPavg was calculated based on MALDI-ToF MS results using the ion counts for the chains in the product. Based on the DPavg and the yield of the homo-oligomerization it was determined that the amino acids can be ranked according to reactivity in the order: Tyr > Leu > Phe > Trp. Thermal degradation of the homo-oligomers shows two degradation steps: at 178-239 degrees C and at 300-330 degrees C. All the products left a significant amount of char ranging from 18-57% by weight at 800 degrees C. Binary co-oligomers were obtained as a polydisperse precipitate with a compositional distribution of the chains. Both the compositional and chain length distribution are calculated from MALDI-ToF mass spectra. By comparing the amount of each amino acid present in the chains it was determined that the amino acids are incorporated with a preference: Leu > Tyr > Phe > Trp. Ternary co-oligomers were also obtained as a precipitate and analyzed by MALDI-ToF MS. The compositional distribution and the chain length distribution were calculated from the MALDI-ToF data. The quantity of every amino acid in the chains was determined. Also determined was the influence on the DPavg when the oligomers were compared with corresponding binary co-oligomers. From the combined results it was concluded that in the co-oligomerization of three amino acids the reactivity preference is Leu > Tyr > Phe > Trp. Thermal degradation of all the co-oligomers showed a weight loss of 2 wt% before the main oligomer degradation step at 300-325 degrees C.
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Interaction between a globular protein, papain and the anionic surfactant, sodium dodecyl sulfate (SDS) has been studied in aqueous medium in detail using conductometric, tensiometric, calorimetric, fluorimetric, viscometric, circular dichroism techniques. The physicochemical properties, e.g. critical micellar concentration (CMC), counterion binding, free energies, enthalpies and entropy of micellization, interfacial adsorption, micellar aggregation number and micellar polarity of SDS have been determined in presence of papain. The results show that the CMC values of SDS increase with the increasing concentration of papain. The energetics of micellization of papain–SDS system is endothermic and the interaction of SDS with papain is an entropy controlled process. Such physicochemical studies in presence of protein are rare. Also, the conformational behavior of papain in aqueous solution has been investigated in the presence of SDS. The results show the high-helical content and unfolded structure of papain in the presence of SDS due to strong electrostatic repulsion.
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An accurate three-dimensional structure is known for papain (1.65 Å resolution) and actinidin (1.7 Å). A detailed comparison of these two structures was performed to determine the effect of amino acid changes on the conformation. It appeared that, despite only 48% identity in their amino acid sequence, different crystallization conditions and different X-ray data collection techniques, their structures are surprisingly similar with a root-meansquare difference of 0.40 Å between 76% of the main-chain atoms (differences < 3σ). Insertions and deletions cause larger differences but they alter the conformation over a very limited range of two to three residues only. Conformations of identical side-chains are generally retained to the same extent as the main-chain conformation. If they do change, this is due to a modified local environment. Several examples are described. Spatial positions of hydrogen bonds are conserved to a greater extent than are the specific groups involved.
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Problem statement: Nowadays, the worldwide increase in diseases has motivated consumers to increase the intake of fruits and vegetables, in response to various research reports indicating that fruits and vegetables can help prevent certain types of illnesses, due to their potentially high antioxidant properties. We evaluated the effect of the stage of ripeness of papaya fruit (Carica papaya L.) on the contents of bioactive components and their relation with antioxidant capacity. Approach: Whole papaya fruit were selected based on their visual ripeness, classifying them in four stages of ripeness (R1, R2, R3 and R4). Physiological and physical-chemical analysis performed included respiration, production of ethylene, firmness, pH, titratable acidity and total soluble solids, color (L*, a*, b*, °Hue, C); Polygalacturonase (PG) and Pectin Methyl Esterase (PME) activity, total phenolic content and antioxidant capacity (measured using DPPH, TEAC and ORAC assays). Results: The antioxidant capacity decreased approximately 27% in the RS4 when using DPPH and TEAC and increased when using ORAC (60.9%). PG activity increased from 8.14 (in RS1)-22.48 U gFW-1 (in RS4) as the stage of ripeness of papaya fruit increased. PME was affected in a similar manner with an activity of 0.5562 U gFW-1, at the end of the ripening storage. A high correlation between PG activity and softening of ripen papayas was observed. Conclusion/Recommendations: It was observed that papaya fruit experienced changes in firmness, which is correlated with activity from two of the main enzymes: PG and PME and with the increase of respiration and production of ethylene. The various stages of ripeness showed very good antioxidant capacity, being higher in RS1, which is correlated with the higher content of phenolic contents found in this ripening stage.