What is "lactacystin"

n. (context organic compound English) A selective proteosome inhibitor found in ''Streptomyces'' bacteria.

Lactacystin is an organic compound naturally synthesized by bacteria of the genus Streptomyces first described in 1991. The first total synthesis of lactacystin was developed by Elias Corey in 1992. Lactacystin binds and inhibits specific catalytic subunits of the proteasome, a protein complex responsible for the bulk of proteolysis in the cell, as well as proteolytic activation of certain protein substrates. It was the first non-peptidic proteasome inhibitor discovered and is widely used as a research tool in biochemistry and cell biology. It covalently modifies the amino-terminal threonine of specific catalytic subunits of the proteasome, a discovery helped to establish the proteasome as a mechanistically novel class of protease: an amino-terminal threonine protease. The molecule is most commonly used as in biochemistry and cell biology laboratories as a selective inhibitor of the proteasome. The molecule is a lactam, or cyclic amide. A number of syntheses of this molecule have been published and there are more than 1,500 citations for lactacystin in PubMed as of 2013.