Skip to main content
. Author manuscript; available in PMC: 2017 Aug 1.
Published in final edited form as: Trends Biochem Sci. 2016 Jul 11;41(8):654–664. doi: 10.1016/j.tibs.2016.06.004

Figure 3.

Figure 3

Long-lived proteins (LLPs) decompose in the body. A common site of deterioration is at asparagine and aspartic acid which can undergo racemization via succinimide intermediates. These are spontaneous events that occur primarily in unstructured regions of the protein, leading to four possible Asp isomers: L-Asp, D-Asp, L-isoAsp, and D-isoAsp. Asp residues converted to isoAsp appear to be stable and undergo little interconversion. In most cells protein isoaspartate methyl transferase (PIMT) can ameliorate Asp racemization by methylating L-isoAsp and D-Asp, enabling the conversion back to L-Asp. Currently this is the only known repair enzyme for the repair of racemised Asp in LLPs.