Out of the following, which is substrate for the rate limiting enzyme of polyamine biosynthesis?

ANS:-Ornithine>>Arginine 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.