SRM is an enzyme which catalyzes the transfer of the propylamine group from S-adenosylmethioninamine to putrescine in the biosynthesis of spermidine. The polyamines putrescine， spermine and spermidine are ubiquitous polycationic mediators of cell growth and differentiation. The SRM protein is one of four enzymes in the polyamine-biosynthetic pathway and completes the final step of spermidine biosynthesis.
