L-isoleucine (Ile)

L-isoleucine is one of the three branched-chain amino acids (BCAAs) and is categorized as an essential amino acid, meaning it cannot be synthesized by the human body and must be obtained through diet. It plays a dual role in metabolism, being both glucogenic and ketogenic, as it is broken down into succinyl-CoA and acetyl-CoA. Beyond its structural requirement in protein synthesis, L-isoleucine is a vital signaling molecule that modulates the mTOR pathway to regulate cell growth, protein turnover, and glucose transport into skeletal muscle. It is also involved in various physiological processes, including wound healing, immune system regulation, and the secretion of several hormones. Clinically, L-isoleucine is significant due to its involvement in metabolic disorders like Maple Syrup Urine Disease (MSUD), where a deficiency in the branched-chain alpha-keto acid dehydrogenase (BCKDH) complex leads to toxic accumulation of the amino acid and its keto-derivatives. In the pharmaceutical industry, L-isoleucine is commonly included in total parenteral nutrition (TPN) formulations and electrolyte solutions to support recovery in critically ill patients. It also exhibits competitive interactions with drugs like Levodopa for transport across the blood-brain barrier via the Large Neutral Amino Acid Transporter (LAT1), which can influence the efficacy of Parkinson's disease treatments.

Other names

(2S,3S)-2-amino-3-methylpentanoic acidIsoleucineL-Ile2-Amino-3-methylvaleric acid

As an essential amino acid, L-isoleucine acts as a substrate for ribosomal protein synthesis and is metabolized into acetyl-CoA and propionyl-CoA for the citric acid cycle. It functions as a nutrient signal that activates the mTORC1 (mechanistic target of rapamycin complex 1) pathway, primarily through its interactions with Sestrin2 and leucyl-tRNA synthetase, which regulate cell growth and protein translation. In therapeutic contexts, it is used in parenteral nutrition to maintain nitrogen balance and prevent muscle wasting.