1. Primary examples are putrescine, cadaverine, spermidine, and spermine . 2. Spermine is the chemical primarily responsible for the characteristic odor of semen.3. Its activity is inhibited by spermine , sphingosine, and several phospholipids. 4. Spermidine is a precursor to further polyamines, such as spermine and its structural isomer thermospermine. 5. For comparison the similar substance spermine , found in semen, is over 3 times as toxic. 6. "' Spermine "'is a polyamine involved in cellular metabolism found in all bacteria. 7. Crystals of spermine phosphate were first described in 1678, in human semen, by Antonie van Leeuwenhoek. 8. Agmatinase hydrolyses agmatine to putrescine, the precursor for the biosynthesis of higher polyamines, spermidine and spermine . 9. Basic amines such as putrescine, spermine , spermidine and cadaverine are responsible for the smell and flavor of semen. 10. :spermine + O 2 + H 2 O \ rightleftharpoons spermidine + 3-aminopropanal + H 2 O 2
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