Friday, March 20, 2015

Study group discussion: Largest protein and the smallest protein in the human body

How many amino acids make up a protein ?

>100 ~ proteins
10-100 ~ polypeptide
<10 ~ peptide

Which protein is smallest in the human body?

Thyroid releasing hormone or TRH should be the smallest protein in the human body, with 234 amino acids. (> 100 amino acids is a protein.)
Smallest polypeptide in the human body should be insulin, with 54 amino acids. (10-100 amino acids is a polypeptide.)
Smallest peptide in the human body should be glutathione, with 3 amino acids. (<10 amino acids is a peptide.)
I concluded these on what I found on Google. Correct me if I'm wrong.

Largest protein is titin in the human body!

Interesting virology fact:-
The largest viruses as Poxviruses measuring 300nm are as large as the smallest bacteria (mycoplasma). The smallest viruses as Parvovirus measuring about 20nm are nearly as small as one of the largest protein molecule, hemocyanin.


  1. no difference in TSH and TRH??? i m feeling CONFUSED! is that TSH the smallest protein or TRH?? as both r different

  2. Insulin is built from 51 amino acids and is one of the smallest proteins in the body. It is structured with two polypeptide chains linked by two disulfide bonds, connecting the amino acid Cysteine to Cysteine. Dr. Said Amin

    1. i agree with Said Amin in terms of 51 Amino acid residues in Insulin.

  3. less thn 40 amino acids will be called poly peptide while more thn 40 amino acid will be called Pretein

    1. Not strictly true. All proteins consist of at least 1 polypeptide (over 20 or so amino acids), but some proteins (functional units!!) have multiple polypeptides in a multi-subunit, **functional** protein (quaternary structure). Proteins, as customarily defined by biochemists, are polypeptides that have a cellular FUNCTION (not just a signaling function) based on their three-dimensional structure.

  4. largest protein is TITIN (34,350aa)
    Smallest proteins is 1L2Y (20aa)

  5. amino acids >35 is called protein while amino acids < 35 is only polypeptide.

  6. This is really great information. I have visited so many blogs however, I found the most relevant info here.


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