<prompt> Out of the following, which is substrate for the rate limiting enzyme of polyamine biosynthesis?AnandamideCadaverineOrnithineHistidine  <response>: ANS:-OrnithineArginine Rate limiting enzyme of polyamine biosynthesis is Ornithine decarboxylase, for which substrate is ornithine. Arginine can also be marked, As arginine is the source of ornithine, by enzyme arginase. Polyamines polycations Major polyamines are: putescine diamine, spermidine triamine spermine tetramine. Roles of polyamines are: Cell growth, survival, regulation and proliferation Used as a growth factor in cell cultures Changes in polyamine levels are associated with aging and diseases. Therapeutic use of polyamine biosynthesis inhibitor:- DFMO Di Fluoro Methyl Ornithine in sleeping sickness hirsuitism. 