Table III.

Characterization of posttranslational modifications of the two-chain TPI

The N termini of the separated chains were determined by sequencing. The C termini were identified by assigning MALDI-TOF mass spectrometry data to cDNA sequence. The A2 chain was characterized after removal of N-terminal pyroglutamic acid (<Q) and N-linked oligosaccharide of paucimannosidic type.

PeakMass ObservedMass CalculatedaN-Terminal SequencebAssigned Structure
DD
1-K22402239KACPRNCDGRIAYEICPRKACPRNCDGRIAYEICPR
1-A21142111ACPRNACPRNCDGRIAYEICPR
A24502(<Q)ICTNcn.a.d
3490e3487<QICTNCCAGTKGCNYFSANGTFICEGESEY
  • a Mass calculated with carboxymethylated Cys residues.

  • b Cys residues identified as carboxymethyl Cys.

  • c Sequence determined after treatment with pyroglutamate aminopeptidase.

  • d n.a., Not assigned.

  • e Mass determined after treatment with N-glycosidase A.