The simplest amino acid. It has the formula NH2
COOH. There are several pathways of glycine biosynthesis. It can be made directly from ammonia, carbon dioxide, and a methyl group donated by the methylating agent N5
methylenetetrahydrofolic acid (mTHFA). In another reaction involving mTHFA, glycine can be formed from serine. A third pathway, from phosphoglyceric acid, involves transamination of glyoxylate. Glycine can be broken down either by reversal of the first or second synthetic pathway, or by deamination to glyoxylate and hence into the TCA cycle via malic acid.
Glycine is one of the basic components of porphyrins, along with *succinic acid
. It is also necessary in purine synthesis.