The structural basis for catalysis and specificity of the X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis.

The X-prolyl dipeptidyl aminopeptidase (X-PDAP) from Lactococcus lactis is a dimeric enzyme catalyzing the removal of Xaa-Pro dipeptides from the N terminus of peptides. The structure of the enzyme was solved at 2.2 A resolution and provides a model for the peptidase family S15.

Coster-kronig decay of the ar2s hole observed by auger-threshold photoelectron coincidence spectroscopy.

The Coster-Kronig lines associated with Ar2s decay have been resolved within the natural linewidth of the 2s hole for the first time. This was possible by a new spectroscopic technique, relying on resonance enhanced double photoionization, Auger-threshold photoelectron coincidence spectroscopy. Contrary to standard Auger spectroscopy, this technique can filter out weak components in Auger spectra corresponding to a well-defined inner-shell state and, furthermore, can achieve a resolution no longer limited by the lifetime of the inner-shell hole.