Proteinogenic Amino Acid - Non-specific Abbreviations

Non-specific Abbreviations

Sometimes the specific identity of an amino acid cannot be determined unambiguously. Certain protein sequencing techniques do not distinguish among certain pairs. Thus, the following codes are used:

• Asx (B) is "asparagine or aspartic acid"
• Glx (Z) is "glutamic acid or glutamine"
• Xle (J) is "leucine or isoleucine"

In addition, the symbol X is used to indicate an amino acid that is completely unidentified.