isoleucine
noun
iso·leu·cine
ˌī-sō-ˈlü-ˌsēn 
: a crystalline, hydrophobic, essential amino acid C6H13NO2 that is obtained in its levorotatory l-form by the hydrolysis of dietary protein and is isomeric with leucine
Examples of isoleucine in a Sentence
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These amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine – collectively necessary for building muscle, producing enzymes and hormones and maintaining healthy tissue.
—
Daryl Austin, USA Today, 21 Mar. 2026
This means there is twice as much leucine as there is isoleucine or valine.
—Lindsay Curtis, Verywell Health, 25 Jan. 2026
BCAAs are three amino acids—leucine, isoleucine, and valine—that aren't naturally made in the body.
—Health, 17 June 2025
Amino acid supplements are typically either EAA (essential amino acids) or BCAA (branched chain amino acids, which are three amino acids—leucine, isoleucine, and valine—that the body cannot produce itself).
—Misaki Kawatsu, Vogue, 10 June 2025
Nine essential amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—are available only through foods or supplements.
—Stacey Colino, Time, 27 May 2025
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Daryl Austin, USA Today, 21 Mar. 2026
This means there is twice as much leucine as there is isoleucine or valine.
—Lindsay Curtis, Verywell Health, 25 Jan. 2026
BCAAs are three amino acids—leucine, isoleucine, and valine—that aren't naturally made in the body.
—Health, 17 June 2025
Amino acid supplements are typically either EAA (essential amino acids) or BCAA (branched chain amino acids, which are three amino acids—leucine, isoleucine, and valine—that the body cannot produce itself).
—Misaki Kawatsu, Vogue, 10 June 2025
Nine essential amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—are available only through foods or supplements.
—Stacey Colino, Time, 27 May 2025
Cite this Entry
“Isoleucine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/isoleucine. Accessed 26 Mar. 2026.
Copy CitationMedical Definition
isoleucine
noun
iso·leu·cine
ˌī-sō-ˈlü-ˌsēn
: a crystalline essential amino acid C6H13NO2 isomeric with leucine
—abbreviation Ile
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