Synthesis, kinetic characterization and X-ray analysis of peptide aldehydes as inhibitors of the 20S proteasomes from Thermoplasma acidophilum and Saccharomyces cerevisiae.

A comparative kinetic characterization of the peptide aldehydes Ac-Leu-Leu-X-H [X = Trp, Tyr and Tyr(tBu)] and Z-Gly-Pro-Gly-Gly-Leu-Leu-Nle-H as inhibitors of the chymotryptic activity of 20S proteasomes from the archaebacterium T. acidophilum and yeast S. cerevisiae revealed significantly differentiated inhibitory potencies that can be rationalized on the basis of X-ray crystallographic data.