Definition for Leucine
From Biology Forums Dictionary
One of the naturally-occurring amino acids; it has a large aliphatic side chain with nonpolar character.
Leucine is a very common residue in proteins (in fact it may be the most common), where it normally forms part of the non-polar interior of folded protins. It tends also to occur more frequently in α-helices. Due to the γ-branched side chain, it is preferred in this context over β-branched residues such as isoleucine or valine that tend to increase steric strain. An α-helical, coiled-coil motif called a "leucine zipper", features leucine residues prominently at the interface between two helices that wrap around each other. In catabolism, leucine is ketogenic, giving rise to acetoacetate and acetyl CoA. Leucine has the codons CUN, UUA, UUG. (Leucine is one of three amino acids with 6 codons; the other two are arginine and serine.) Symbols Leu, L.
pKa values: α-COOH, 2.33; α-NH3+, 9.74.
