General base-general acid catalysis by terpenoid cyclases.

摘要: Terpenoid cyclases catalyze the most complex reactions in biology, that more than half of substrate carbon atoms often undergo changes bonding during course a multistep cyclization cascade proceeds through multiple carbocation intermediates. Many mechanisms require stereospecific deprotonation and reprotonation steps, cascades are terminated by to yield an olefin product. The first bacterial terpenoid cyclase crystal structure was pentalenene synthase from Streptomyces exfoliatus UC5319. This generates hydrocarbon precursor pentalenolactone family antibiotics. structures other reveal predominantly nonpolar active sites typically lacking amino acid side chains capable serving general base-general functions. What chemical species, then, enables Bronsted acid-base chemistry required catalytic these enzymes? likely candidate for such is co-product inorganic pyrophosphate. Here, we briefly review biological nonbiological systems which phosphate its derivatives serve base functions catalysis. These examples highlight fact activities comparable chains.