Question

What is β-Carotene? Why is β-Carotene important? How is β-Carotene metabolized?

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Answer 1

• Carotenes are photosynthetic pigments which are terpenoids and is abundant in plants. Humans obtain this from plants. β-carotene is a member of carotene, which is a red orange pigment and is synthesized from geranyl geranyl phosphate. It is rich in vegetables like carrot.
• β-carotene is a precursor of vitamin A, which is important for growth, maintaining immune system,proper eye sight etc. It is also an antioxidant which scavenge free radicals from body and reduce the risk of cancer.
• In metabolism of beta carotene- it is cleaved at 15,15' double bond by enzymes like CMOI and yield two molecules of retinaldehyde ,this is then oxydised into retinoic acid by enzyme aldehyde dehydrogenase 1 ,further oxydisation is by cytochrome p450 family enzymes.
• Alternatively retinaldehyde an also be  reduced to retinal by different form of alcohol dehydrogenase (ADH)and then further esterified into retinal esters by enzyme LRAT.
• If β carotene  is cleaved at 9,10'double bonds by CMOII apo carotinal can be formed.
• β-carotene is absorbed from small intestine to the body , intestine have enzymes like CMOI to break down it. Beta carotene is highly lipophilic and non polar so is circulated along with lipoprotein.They get incorporated into hydrophobic core of lipoprotein like LDL and lipoprotein facilitate its transport from intestine to various tissue of the body.
• Within the tissues it is used or stored . Liver is the major organ that store and is in the form of retinal esters, followed by adipose tissue, kidney, skin and lungs.