Papain is the dried and purified latex of the green fruits and leaves of Carica papaya L., belonging to family Caricaceae.
PAPAIN
Synonyms
Papayotin, vegetable pepsin, tromasin, arbuz.
Biological Source
Papain is the dried and purified latex of the green fruits
and leaves of Carica papaya L.,
belonging to family Caricaceae.
The plant is cultivated in Sri Lanka, Tanzania, Hawai, and
Florida. The plant is 5–6 m in height bearing fruits of about 30 cm length and
a weight up to 5 kg. The epicarp adheres to the orange-coloured, fleshy
sarcocarp, which surrounds the central cavity. This cavity contains a mass of
nearly black seeds.
Preparation
It is distributed throughout the plant, but mostly
concentrated in the latex of the fruit.
The latex is obtained by making two to four longitudinal
incisions, about 1/8 inch deep, on the surface on four sides of nearly mature
but green fruits while still on the tree. The incisions are made early in the
morning, at intervals of three to seven days. The latex flows freely for a few
seconds but soon coagulates. The exudate is collected in nonmetallic
containers. The latex is dried as soon as possible after collection. Rapid drying
or exposure to sun or higher temperature above 38°C produce dark colour product
with weak in proteolytic activity. The use of artificial heat yields the better
grade of crude papain. The final product should be creamy white and friable. It
is sealed in air-tight containers to prevent loss of activity. If 10% common
salt or 1% solution of formaldehyde is added before drying, the product retains
its activity for many months.
Fully grown fruits give more latex of high enzyme potency
than smaller or immature fruits. The yield of Papain varies from 20 to 250 g
per tree. The yield of commercial Papain from latex is about 20%.
Characteristics
Papain occurs as white or greyish-white, slightly hygroscopic powder. It is incompletely soluble in water and glycerol. It may digest about 35 times its weight of lean meat. Best grades render digestion of 200–300 times their weight of coagulated egg albumin in alkaline media. A temperature range of 60–90°C is favourable for the digestive process with 65° the optimum point. Best pH is 5.0, but it functions also in neutral or alkaline media. It is activated by reduction (HCN and H2S) and inactivated by oxidation (H2O2, iodoacetate).
Chemical Constituents
Papain contains several enzymes such as proteolytic enzymes
peptidase I capable of converting proteins into dipeptides and polypeptides,
rennin-like enzyme, clotting enzyme similar to pectase and an enzyme having a
feeble activity on fats.
The enzymes, papain, papayaproteinase, and chymopapain,
have been isolated in crystalline form from the latex. Papain is atypical
protein digesting enzyme with isoelectric point. It contains 15.5% nitrogen
and 1.2% sulphur. Crystalline papain is most stable in the pH range 5–7 and is
rapidly destroyed at 30°C below pH 2.5 and above pH 12. Papain is a protein of
212 amino acids and having a molecular weight of about 23,000 daltons. It is
resistant to heat, inactivated by metal ions, oxidants and reagents which react
with thiols, and is an endopeptidase activated by thiols and reducing moieties,
for example, cysteine, thiosulphate, and glutathione.
The leaves possess dehydrocarpaines I and II, fatty acids,
carpaine, pseudocarpaine, and carotenoids.
The fruits yield lauric, myristoleic, palmitoleic and
arachidic acids, malonated benzyl-p-o-glucosides, 2-phenyl ethyl glucoside, and
4-hydroxy-phenyl-2-ethyl glucoside.
Uses
Papain is used to prevent adhesions; in infected wounds;
internally as protein digestant, as anathematic (nematode), to relieve the
symptoms of episiotomy (incision of vulva), in meat industry for tenderizing
beef, for treatment of dyspepsia, intestinal and gastric disorders, and diphtheria,
for dissolving diphtheria membrane; in surgery to reduce incidence of blood
clots where thromboplasma is undesirable and for local treatment of buccal,
pharyngeal, and laryngeal disorders.
It is used in digestive mixtures, liver tonics, for reducing
enlarged tonsils, in prevention of postoperative adhesions, curbuncles, and
eschar burns. It is an allergic agent causing severe paroxysmal cough,
vasomotor rhinitis and dyspnea. It is a powerful poison when injected
intravenously. In industry it is used in the manufacture of proteolytic
preparations of meat, lever, and casein, with dilute alcohol and lactic acid
as meat tenderizer, as a substitute for rennet in cheese manufacture, in
brewing industry for making chill-proof bear, for degumming natural milk, in
preparation of tooth pastes and cosmetics, in tanning industry for bathing skin
and hides, and as an ingredient in cleansing solutions for soft contact lenses.
Test
Papain is reacted with a gelatin solution at 80°C in the
presence of an activating cysteine chloral hydrate solution for an hour. The
solution is cooled to 4°C for long time. The treated solution must not regel in
comparison to a blank solution under identical con-ditions.
Adulteration
Commercial papain is often adulterated with arrowroot
starch, dried milk of cactus, gutta percha, rice flour, and pepsin.
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