e.carotenoids and enzymology

8/7/2019 e.Carotenoids and enzymology

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14 March 2011

Magister BiologiUKSW

Biologi Molekuler

Karina Lewerissa


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Most widely distributed group of pigmentsoccurred naturally in large quantities

Have structural diversity and variousfunctionsNot produced by human body650 different carotenoids

Lipid solubleTwo types of carotenoids:Xanthophylscarotenes


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-carotene

-carotene

Lycopene

lutein

OH

OH

zeaxanthin

OH-cryptoxanthin


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Name CharacteristicsP hytofluene Acyclic, colorless

Lycopene Acyclic, red

-Carotene Acyclic, light yellow

-Carotene Monocyclic (1 ring), red -orange

-Carotene Monocyclic (1 ring), red -orange

-Carotene Bicyclic (2 rings), orange

-Carotene Bicyclic (1 ring, 1 ring), yellow

-Cryptoxanthin Bicyclic (2 rings), orange

-Cryptoxanthin Bicyclic (1 ring, 1 ring), yellow

Zeaxanthin Bicyclic (2 rings), yellow -orange

Lutein Bicyclic (1 ring, 1 ring), yellow

Violaxanthin Bicyclic, yellow


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At least seven conjugated double bonds are needed for thecarotenoids to impart color

The intensity of food color depends on which carotenoids arepresent, their concentrations, physical states, and the presence orabsence of other plant pigments such as chlorophyll

Carotenoids containing retinoid structures ( -ionone rings), suchas the -and -carotenes, serve as precursors of provitamin A

Carotenoids can act as good singlet oxygen quenchers and freeradical scavengers due to the many double bonds present in theirstructures


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P oor and low solubilityUnstable in the presence of light and oxygen

Serve as oxygen singlet quencherFor most carotenoids, three peaks or twopeaks and a shoulder absorb in the range of

400 to 500 nm.

Panjang gelombang / nm

A b s o r b a n s i

421

444

471

448425

nangka segarkeripik nangka

350 400 450 500 550 6000

0.4

0.8

1.2


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FunctionLight AbsorptionP hotosynthesisP rovision of ColorP hotoprotection

Vitamin A P recursors


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-Carotene plays a crucial role in humanhealth since it is the major source of vitamin

A for most people throughout the world

It has vitamin A activity: 1 g of -carotenecorresponds to 1.67 million IU of vitamin Aand the vitamin activity of 0.6 mg of -carotene is almost equivalent to 0.3 mg of vitamin A.


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Copyright 2005 Wadsworth Group, a division of Thomson Learning


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Conversion beta-carotene to retinolConversion beta-carotene to retinol


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R oles in the body Vitamin A in proteinsynthesis and cell differentiation



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F-Carotene

Chylomicrons

Small intestine

Parenchymalcells Stellate cell

(retinyl palmitate)

Othercells Epithelia

Eye(11-cis-retinal)

+ RBP

Liver

R etinol


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carotene cleavage enzymewas identified in the intestines of rats, hogs

chickens, and humans and in rat liver.The early literature indicates that intestinalcarotene 15,15 -dioxygenase requires ferrousiron for activity and that this enzyme isextremely sensitive to the presence of metalchelators like o-phenanthroline and ,-bipyridyl


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The Km and V m ax of the enzy m e for -carotenewere 7 M and 10 nmol retinal/mg min

The pH optimum for the reaction was in theslightly alkaline range


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FIG. 1.Coomassie and silver stain and immunoblotting of purifiedhuman BCO and S. frugiperda 9 insect cell extracts. BCO was purified with Co2 columnchromatography described under Experimental P rocedures. Aliquots of homogenates

from uninfected ( lane 1, 10 g) or infected (lane 2, 10 g) insect cells and purified BCO (lane 3, 100 ng; lane 4, 650 ng; lane 5, 20 ng) were subjected to SDSpolyacryla m ide gelelectrophoresis. A, protein detection was perfor m ed by Coomassie Brilliant Blue R ( lanes 1 3) and silver staining (lane 4). B, proteins weretransferred to a nitrocellulose membrane and incubated with 10 g/ml of mAb -1-11, and theantibody -antigen complexes were visualized by a chemiluminescence method as described

under ExperimentalP

rocedures. The film was exposed for 10 s. The positions of prestained molecular size markers are shown on the left.


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FIG. 2. I n vitro time course experiment with purified BCO and - carotene as substrate. Reaction velocity (pmol product formed perreaction) as a function of time (min) is plotted for a reaction with 60 ngof purified BCO and 2.5 M -carotene at 37 C. The assays wereperformed as described under Experimental P rocedures, and product

quantitation was performed by reverse -phase HP

LC analysis as describedunder Experimental P rocedures.


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Bioavailability is commonly defined as thefraction of the ingested pigment that isabsorbed and is available in the bloodstream forits utilization in normal physiological function orfor storage

The bioaccessibility of a compound can bedefined as the result of complex processesoccurring in the lumen of the gut to transfer thecompound from a non -digested form into apotentially absorbable form.


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F actors Influencing Bioaccessibility of Pigments from F oodsPhysicochemical properties of compoundLipophilic characterConfigurationDegree of linkageRelease of compound from food matrixType of food matrixSubcellular location of compoundFood processing

Intraluminal factorsNutrients: lipids, fibers, other carotenoidsBile saltspHMicroflora


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L idqvist. A. and Andersson, S. Biochemical Properties of Purified RecombinantHuman Carotene 15,15 -M onooxygenase. The Journal of Biological Chemistyr.Vol. 277., No. 26 Issue of June 28, 23942 - 23946.

e.carotenoids and enzymology

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