Thermospermine synthase

Thermospermine synthase (EC 2.5.1.79, TSPMS, ACL5 (ACAULIS5), SAC51) is an enzyme with systematic name S-adenosylmethioninamine:spermidine 3-aminopropyltransferase (thermospermine synthesizing). This enzyme catalyses the following chemical reaction

S-adenosylmethioninamine + spermidine ⇌ S-methyl-5'-thioadenosine + thermospermine + H⁺

This enzyme is required for correct xylem specification through regulation of the lifetime of the xylem elements.