Figure 2.

Prenylation, carboxymethylation and decarboxymethylation of K-Ras4B. The addition of a 15 carbon tail in the form of a farnesyl prenly group or 20 carbon tail in the form of a geranylgeranyl prenyl group to C185 is catalyzed by farnesyltransferase enzyme (FTase) and geranylgeranyltransferase (GGTase), respectively. This event is followed by two step reaction involving the hydrolysis of the–VIM portion of the CaaX motif by Ras converting enzyme 1 (RCE1) and the exposure of the carboxylic terminal of C185 for esterification by isoprenylcysteine carboxyl methyltransferase (Icmt). The latter step is a reversible step that can be catalyzed by carboxylesterases called Prenylated/polyisoprenylated methylated protein methyl esterases (PMPEases).