Fruit Ripening and Protease Activity

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Fruit RipeningandProtease Activity
Janet Byun EDTEP 586 December 8, 2005
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QUESTION How does protease activity change as
fruits ripen?

• BACKGROUND RESEARCH
• Fruit Ripening Process
• Enzymes
• Proteases

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Enzymes
Fruit Ripening Process

• Irreversible biochemical process between late
  maturation, early senescence.
• Changes in color, texture, aroma, flavor.
• Initiated by ethylene
• A gaseous plant hormone produced by the fruit.
• Production rate increases with ripening.
• Induces/regulates genes that encode for enzymes.

• Are proteins that catalyze reactions in
  metabolism.
• Bind substrates at active sites, form ES-complex.
• Not consumed or altered by reactions.
• Found in raw fruits and vegetables.

Proteases

• Are enzymes that hydrolyze peptide bonds of
  proteins.
• Banana, mango, papaya contain a protease called
  papain kiwi contains actinidin pineapple
  contains bromelin. These proteases are known to
  break down proteins in ripening tissues.

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HYPOTHESIS Riper fruits have increased protease
activity compared to less ripe/unripe fruits.
INITIAL MODEL
Theoretical black text in white boxes
unripe fruit
produces
H2CCH2
(ethylene)
induces/turns on
producing
enzymes
genes
increasing
(for enzyme synthesis)
degrade
parts of fruit
resulting in
(chlorophyll, acids, starches, pectin, proteins,
etc.)
ripening fruit
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METHODS

• Prepared four petri dishes with 5mm thickness of
  gelatin each.
• Created five 8.5mm width wells.

• Obtained 20 fruits with proteases known to
  degrade protein in gelatin.
• 4 bananas
• 4 kiwis
• 4 mangos
• 4 papayas
• 4 pineapples

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METHODS (continued)

• DAY 1 Collected fresh fruit juice from 1-day old
  fruits of each type of fruit.

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METHODS (continued)

• Placed 5 drops of each type of fresh fruit juice
  into assigned, numbered wells.
• C water (for control)
• 1 banana
• 2 kiwi
• 3 mango
• 4 papaya
• 5 pineapple

1
5
2
C
4
3

• Petri dishes with filled wells then sat for 5
  hours at room temperature. Diameters of wells
  measured and recorded.
• Procedure repeated for 3-day old, 5-day old, and
  7-day old fruits.

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ASSUMPTIONS

• Ethylene source purely from fruit not from
  surroundings.
• Temperature and ventilation of environment for
  fruits constant.
• No wounds, pests, or pathogens affecting fruits.
• Breakdown of gelatin strictly due to proteases in
  fruits.
• Proteases active under room temperature.
• 7 days would be a sufficient amount of time to
  collect data for ripening.

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DATA

• C Water
• 1 Banana
• 2 Kiwi
• 3 Mango
• 4 Papaya
• 5 Pineapple

1
1
2
2
5
5
C
C
3
3
4
4
DAY 3
DAY 1
1
1
5
2
2
5
C
C
3
3
4
4
DAY 5
DAY 7
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DATA (continued)
(1) Banana
(5) Pineapple
(2) Kiwi
(C) Water (control)
(3) Mango
(4) Papaya
DAY 1
diameter of wells (mm)
Day (C) Water (1) Banana (2) Kiwi (3) Mango (4) Papaya (5) Pineapple
1 8.5 8.8 12.5 10.1 9.2 12.8
3 8.7 9.0 13.1 9.8 9.5 13.0
5 8.5 10.0 13.5 11.4 11.2 15.5
7 8.3 9.7 14.4 13.0 12.5 16.0
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DATA (continued)
Riper fruits had increasing protease activity
present compared to less ripe fruits.
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CULMINATING ARGUMENT
Claim - Ripe fruits have an increase in protease
activity compared to less ripe/unripe fruits
because as fruits ripen, they produce
increasing amounts of ethylene, signaling more
enzyme genes to be translated and transcribed,
and thus more enzymes to be produced to
hydrolyze proteins. Explanation - Data collected
and represented in my graph is
evidence supporting an increasing trend in
protease activity as fruits ripen.
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HYPOTHESIS Riper fruits have increased protease
activity compared to less ripe/unripe fruits.
INITIAL MODEL
Theoretical black text in white boxes
unripe fruit
produces
H2CCH2
(ethylene)
induces/turns on
producing
enzymes
genes
increasing
(for enzyme synthesis)
degrade
parts of fruit
resulting in
(chlorophyll, acids, starches, pectin, proteins,
etc.)
ripening fruit
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Explanation (continued) - REVISED MODEL

wound/pests/pathogens
temperature increase
unripe fruit
methionine
produces
reacts with
to be converted to
H2CCH2
oxygen
(ethylene)
inhibits growth of/diffuses into
induces/turns on
produce
enzymes
genes
(for enzyme synthesis)
increases
catalyze
Amylase starch --gt sugar Pectinase pectin --gt
less pectin Kinase acids --gt neutral Protease
proteins --gt amino acids
biochemical reactions
degrade
results in
fruit tissues
(chlorophyll, acids, starches, pectin, proteins,
etc.)
ripening fruit
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