So we all know that humans cannot digest hair because "we don't have the enzyme needed to digest keratin which is the main component of hair".
But I wonder, if this is true, then why can we digest meat and other cell types? Don't forget that keratin fibers or intermediate filaments are part of the cytoskeleton too so we shouldn't be able to eat meat and stuff like this.
Thank you very much.
All the enzymes are biocatalyst and active only in solluble form.So Keratin/cytoskeletal protein in cells is in both the solluble and insolluble form. However hair keratins are essentially insolluble in water. (Its not true that humans dont have enzyme for digestion of keratin proteins) If one can make hair keratins in solluble-form humans can digest it with trypsin/pepsin.
Deepak Kanojia: You said inside the cell, keratin also exists in insoluble form too. Then what make this keratin different from the insoluble keratin in hair?
So there are >50 different, functional Keratins in humans. Keratins in Hair are insolluble because of multiple disulphide bonds in keratin proteins.
Ahh, I see. I thought there were only 1 type of keratin but it turns out to be a family of keratin. The name confused me!
Thank you very much.
Can we digest our own hair?
I thought we could not?
But if we can make disulphide bonds while growing hair,
why can we not digest them when we eat hair?
Your question is more to do with evolution according to me. As a background - The disulphide bonds in protein occurs throughout nature for proper folding of proteins - hence proper function. Classic example is an antibody which has heavy and light chains connected through disulphide bonds. That being said, digestion of proteins is important for absorption of amino acids, hence peptide bonds need to be degraded.
To the best of my knowledge there is no thioredoxin or thiol reductase in digestive enzymes.
Hence is important to make proteins which function properly inside/outside the cells, but (I believe) we don’t need enzyme to degrade S-S bonds just for the heck of it. Moreover S-S bonds are essentially through cysteine – a non-essential amino acid which body can synthesize, hence from an evolutionary stand point we don’t need thioreductase/ thioredoxins to degrade S-S to absorb cysteine (also not all cysteines are in the form of S-S bonds).
I thought enzymes were catalysts of reactions.
Which way a reaction goes depends on
external factors controlling reactants and resultants.
So if a catalyst can create s-s bonds then it can also break them.
So if we can make hair we can also unmake it.
Why can we not dissolve keratin by breaking the s-s bonds?
Note the 'insoluble' has only one l'.
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