PCA stands for L-2-Pyrrolidone-5- Carboxylix acid,
which is another way of saying
L-Pyroglutamic Acid (Is the light appearing?)
which is a cyclic form of L-Glutamic Acid,
which is a post-translational modification that
can occur when proteins are expressed in recombinant
DNA systems e.g. E.coli, and cause serious grief when
attempting to undertake N-terminal sequencing.
Today I would use "PYR" instead of "PCA" but
Brookhaven continue to use the latter.
This is effectively an N-terminal proline]
incorporating the NH3 in to the ring, hence
the sequencing problem.
Question: What has happened to the
two carbon atoms (gamma and delta)
required to form the ring?
Jim Pitts.