structural:summarization, information:classification
N -methyl-pyrrolinium cation

The biosynthesis begins with L- Glutamine, which is derived to L- ornithine in plants. The major contribution of L-ornithine and L- arginine as a precursor to the tropane ring was confirmed by Edward Leete. Ornithine then undergoes a pyridoxal phosphate -dependent decarboxylation to form putrescine. In some animals, the urea cycle derives putrescine from ornithine. L-ornithine is converted to L-arginine, which is then decarboxylated via PLP to form agmatine. Hydrolysis of the imine derives N -carbamoylputrescine followed with hydrolysis of the urea to form putrescine. The separate pathways of converting ornithine to putrescine in plants and animals have converged. A SAM-dependent N -methylation of putrescine gives the N -methylputrescine product, which then undergoes oxidative deamination by the action of diamine oxidase to yield the aminoaldehyde. Schiff base formation confirms the biosynthesis of the N -methyl-Δ -pyrrolinium cation.