13-Hydroxylupanine in the Biosynthesis of Quinolizidine Alkaloids
Wink M. Journal of chemical ecology, 2019, 45(2), 109-115.
Quinolizidines (QAs) are an important class of alkaloids that have been extensively studied as defense chemicals in plants. The biosynthetic process of QA involves the following important aspects:
· The process of QA biosynthesis begins with the amino acid lysine, which is decarboxylated by lysine decarboxylase (LDC) to form the diamine cadaverine.
· Cadaverine is then desaminated either by a transaminase or an oxidase to produce 5-aminopentanal. Through a complex reaction, the amino group of 5-aminopentanal reacts with the aldehyde function of two additional molecules of 5-aminopentanal to form a tetracyclic quinolizidine ring skeleton, which can be further converted into sparteine or lupanine.
· Hydroxylation of lupanine to 13-hydroxylupanine allows for the generation of ester alkaloids by tigloyl-CoA: 13-hydroxylupanine O-tigloyl transferase.
· Methyl groups can be transferred to free nitrogen atoms in certain QA molecules, such as cytisine, by S-adenosyl-Lmethionine: N-methyltransferase.
· Genes for LDC, cadaverine oxidase, and tigloyl-CoA: 13-hydroxylupanine O- tigloyl transferase have been discovered. Currently, the transcriptomes of QA-producing plants are being analyzed using RNASeq to discover additional genes involved in QA synthesis, storage, and transport.