Spermidine is a polyamine compound () originally isolated from semen and also found in ribosomes and living tissues and has various metabolic functions in organisms.

Function

Spermidine synchronizes an array of biological processes, (such as Ca<sup>2+</sup>, Na<sup>+</sup>, K<sup>+</sup> -ATPase) thus maintaining membrane potential and controlling intracellular pH and volume. Spermidine regulates biological processes, such as Ca<sup>2+</sup> influx by glutamatergic N-methyl-<small>D</small>-aspartate receptor (NMDA receptor), which has been associated with nitric oxide synthase (NOS) and cGMP/PKG pathway activation and a decrease of Na<sup>+</sup>,K<sup>+</sup>-ATPase activity in cerebral cortex synaptosomes.

Spermidine is a longevity agent in mammals due to various mechanisms of action, which are just beginning to be understood. Autophagy is the main mechanism at the molecular level, but evidence has been found for other mechanisms, including inflammation reduction, lipid metabolism, and regulation of cell growth, proliferation, and death. Spermidine has been theorized to promote autophagy via the MAPK pathway by inhibiting phosphorylation of raf,

Biosynthesis

left|thumb|400x400px|Biosynthesis of spermidine and spermine from putrescine. Ado = 5'-adenosyl.

Spermidine is an aliphatic polyamine. In plants and some bacteria, spermidine synthase (SPDS) catalyzes its formation from putrescine. It is a precursor to other polyamines, such as spermine and its structural isomer thermospermine.

Many of the organisms that make up the gut microbiota in humans do not contain the SPDS enzyme, for example the ϵ-proteobacteria.

The intermediate, carboxyspermidine, is then decarboxylated by carboxynorspermidine decarboxylase:

  • Binds and precipitates DNA
  • Polyamine plant growth regulator

Sources

Good dietary sources of spermidine are aged cheese, mushrooms, soy products, legumes, corn, and whole grains. Spermidine is plentiful in a Mediterranean diet.

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Uses

  • Spermidine can be used in electroporation while transferring the DNA into the cell under the electrical impulse. May be used for purification of DNA-binding proteins.
  • Spermidine is also used, along with calcium chloride, for precipitating DNA onto microprojectiles for bombardment with a gene gun.
  • Spermidine has also been reported to protect the heart from aging and prolong the lifespan of mice, while in humans it was correlated with lower blood pressure. It also was found to reduce the amount of aging in yeast, flies, worms, and human immune cells by inducing autophagy.
  • Spermidine may play a role in male and female fertility. Fertile men have higher spermidine levels than men who are infertile, and spermidine supplementation has been shown to help maintain a healthy hormone balance and reduce oxidative stress.
  • Spermidine is commonly used for in vitro molecular biology reactions, particularly, in vitro transcription by phage RNA polymerases, in vitro transcription by human RNA polymerase II, and in vitro translation.
  • Spermidine increases specificity and reproducibility of Taq-mediated PCR by neutralizing and stabilizing the negative charge on DNA phosphate backbone.

References

  • Safety Data Sheet