Relationship of the expression of the S20 and L34 ribosomal proteins to XXXX biosynthesis in @entity526 .

@entity7222 @entity7226 @entity7228 @entity4664 @entity369 @entity526
@entity4664 biosynthesis in @entity526 is regulated transcriptionally and post-translationally. Antizyme and ribosomal proteins S20 and L34 participate in post-translational inhibition of the @entity4664 biosynthetic enzymes @entity7222 and @entity369 decarboxylase. The aim of the present study was to investigate the significance of S20 and L34 in @entity4664 regulation in vivo. In vivo overexpression of S20 and L34 lowered the activities of @entity7222 and @entity369 decarboxylases and decreased total @entity4664 production. The levels of @entity7226 , a related @entity7228 whose synthesis is not regulated by S20 and L34, did not decrease but increased. The diminished @entity7222 and @entity369 decarboxylase activities are shown to result from reversible post-translational inhibition since the enzymes could be reactivated to normal levels upon titration of the inhibitors. The effects were specific as overexpression of eight other ribosomal proteins had no influence. Overexpression of @entity7222 decarboxylase results in elevated @entity4664 production and it increases S20 and L34 levels but not those of other ribosomal proteins. @entity7222 depletion decreases S20 and L34 to normal levels in the @entity7222 decarboxylase overproducing cells. Immunoprecipitation experiments coupled with immunoblots indicated that @entity7222 and @entity369 decarboxylases physically interact with S20 and L34. This study shows that ribosomal proteins S20 and L34 can inhibit @entity7222 and @entity369 decarboxylases and @entity4664 biosynthesis in vivo. It is concluded that, unlike other basic ribosomal proteins and polycationic compounds which inhibit the activities of these enzymes only in vitro, S20 and L34 are biologically relevant in the regulation of the @entity4664 biosynthetic pathway.
