Alanine

Alanine is one of the simplest amino acids, with a methyl group (–CH₃) as its side chain. It is encoded by the codons GCU, GCC, GCA and GCG and is one of the most abundant amino acids in proteins.

Its small, nonpolar side chain fits almost anywhere in a folded protein. Alanine is particularly common in the alpha helix, which it stabilizes, and it is used in experiments called alanine scanning, where each position of a protein is swapped for alanine in turn to find which side chains are important. It was first isolated from silk protein in 1879.

The body makes alanine from pyruvate, the end product of glycolysis, by transferring an amino group in a reaction catalyzed by the enzyme alanine aminotransferase. In the glucose-alanine cycle, muscles release alanine, which the liver takes up and converts back to glucose, carrying nitrogen away from muscle. Because it can be made, it is a non-essential amino acid.

Blood levels of alanine aminotransferase (ALT) are used as a test for liver damage, since the enzyme leaks out of injured liver cells. Beta-alanine is a related compound that is a part of carnosine and of vitamin B5. Alanine is one of the standard building blocks of proteins, specified by the genetic code, and it has a close relative in serine, which has a hydroxyl group in place of one hydrogen of the methyl.

• Amino Acid — the class it belongs to
• Alpha Helix — a structure it stabilizes
• Glycolysis — the pathway that supplies its precursor