(R)and (S)Configuration OH HO CH; NH2 HN CH; natural alanine unnatural alanine Both enantiomers of alanine receive the same name in the IUPAC system:2-aminopropanoic acid. Only one enantiomer is biologically active.In alanine only the left enantiomer can be metabolized by the enzyme. Need a way to distinguish between them. 2013 Pearson Education,Inc. Chapter 5 12© 2013 Pearson Education, Inc. (R) and (S) Configuration • Both enantiomers of alanine receive the same name in the IUPAC system: 2-aminopropanoic acid. • Only one enantiomer is biologically active. In alanine only the left enantiomer can be metabolized by the enzyme. • Need a way to distinguish between them. Chapter 5 12