Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Absorption rate - oral (%):
Absorption rate - dermal (%):
Absorption rate - inhalation (%):

Additional information

Absorption and distribution

L-leucine is an essential, branched-chain amino acid. The biosynthesis of L-leucine occurs in plants and microorganisms. Animals receive the required amount of L-leucine via their diet. Leucine is absorbed from the gastro-intestinal tract either as the free amino acid or as a constituent of peptides. Subsequently, L-leucine is transported to the liver and used as protein building blocks. Furthermore, some L-leucine is also distributed via the blood to various body tissues, such as muscle and adipose tissue.


L-leucine participates in both anabolic (protein synthesis) and catabolic processes (depicted in the BCAA catabolic pathway described by Brosnan and Brosnan).


Elimination of L-leucine starts by deamination of the amino acid. The amino group enters the Krebs-Henseleit cycle and is excreted as urea in the urine. The remaining fragment of the amino acid can be transformed into acetyl CoA as described by the BCAA catabolic pathway as elaborated by Brosnan and Brosnan.