Isoaspartyl group

Isoaspartyl group 84 Isobutyraldehyde, tautomerism 45 Isobutyryl-CoA mutase 872 Isocitrate 516s, 686s, 704s... 

Aswad DW. Stoichiometric methylation of porcine adrenocorticotropin by protein carboxyl methyltransferase requires deamidation of asparagine 25. Evidence for methylation at the alpha-carboxyl group of atypical L-isoaspartyl residues. J Biol Chem 1984 259 10714-10721. 

The and y-carboxyls of Asp and Glu always require protection in classical SPPS or are activated and form a peptide bond with the free amine leading to the formation of a mixture of peptides. An exception to this practice is the use of a C-terminal Asp or Glu attached to the solid support via the side chain, in which case the a-carboxylate is protected. When the desired product is the isoglutamyl or isoaspartyl peptide, protection of the C -carboxyl is required. Benzyl (Bzl) type or t-butyl ( Bu) groups have most commonly been used for the protection of side-chain carboxylates in SPPS based on t-butyloxycarbonyl (Boc) and 9-fluorenylmethoxycarbonyl (Fmoc) A-terminal protection, respectively. 

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