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Spermidine/spermine N(1)-acetyltransferase (SPD/SPM acetyltransferase) is a rate-limiting enzyme in the catabolic pathway of polyamine metabolism. It catalyzes the N(1)-acetylation of spermidine and spermine and, by the successive activity of polyamine oxidase , spermine can be converted to spermidine and spermidine to putrescine . [ 7 ]
Spermine is synthesized from the reaction of spermidine with SAM in the presence of the enzyme spermine synthase. The polyamines undergo rapid interconversion in the polyamine cycle, in which putrescine leads to synthesis of spermidine and spermine, with degradation of these polyamines to form putrescine, which can begin the cycle again. [16]
Spermine is a polyamine involved in cellular metabolism that is found in all eukaryotic cells. The precursor for synthesis of spermine is the amino acid ornithine . It is an essential growth factor in some bacteria as well.
It is a precursor to other polyamines, such as spermine and its structural isomer thermospermine. Spermidine synchronizes an array of biological processes, (such as Ca 2+ , Na + , K + -ATPase) thus maintaining membrane potential and controlling intracellular pH and volume.
Polyamines provide protection against heavy metals such as inhibiting Cadmium uptake or its entry into the cells because exogenous polyamines are mainly allocated to the apoplast. Spermidine and spermine, kinds of polyamine, are found in reducing cadmium toxicity in rice.
Another major role of SAM is in polyamine biosynthesis. Here, SAM is decarboxylated by adenosylmethionine decarboxylase (EC 4.1.1.50) to form S-adenosylmethioninamine. This compound then donates its n-propylamine group in the biosynthesis of polyamines such as spermidine and spermine from putrescine. [9] SAM is required for cellular growth and ...
Spermine synthase is an enzyme involved in polyamine biosynthesis. It is present in all eukaryotes and plays a role in a variety of biological functions in plants [ 3 ] Its structure consists of two identical monomers of 41 kDa with three domains each, creating a homodimer formed via dimerization .
This enzyme potentially represents a new class of catabolic enzymes in the mammalian polyamine metabolic pathway capable of the efficient oxidation of polyamines. More than five transcript variants encoding four active isoenzymes have been identified for this gene, however, not all variants have been fully described.