Isoleucine

Abbrev. I Ile
Full Name Isoleucine
Side chain type
hydrophobic
Mass
131.17
pl
6.05
pK1(α-COOH)
2.32
pK2(α-+NH3)
9.67

Side chain -CH(CH3)CH2CH3
Hydro- phobic
yes
Polar
no
Charged
no
Small
no
Tiny
no
Aromatic or Aliphatic
Aliphatic
van der Waals volume
124
Codon
AUU, AUC, AUA
Occurrence in proteins (%)
5.3

Remarks: Essential for humans. Isoleucine, leucine and valine have large aliphatic hydrophobic side chains. Their molecules are rigid, and their mutual hydrophobic interactions are important for the correct folding of proteins, as these chains tend to be located inside of the protein molecule.

Isoleucine is one of the 20 standard amino acids, and is coded for in DNA. Its chemical composition is identical to that of leucine, but the arrangement of its atoms is slightly different, resulting in different properties. Nutritionally, in humans, isoleucine is an essential amino acid. Isoleucine is a hydrophobic amino acid.

Isoleucine has two chiral centers; therefore there are four possible stereoisomers of isoleucine and two possible diastereomers of L-isoleucine. However, isoleucine present in nature exists in one enantiomeric form, (2S,3S)-2-amino-3-methylpentanoic acid.

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