Alkaloid Biosynthesis: Metabolism and Trafficking

Abstract

Alkaloids represent a highly diverse group of compounds that are related only by the occurrence of a nitrogen atom in a heterocyclic ring. Plants are estimated to produce approximately 12,000 different alkaloids, which can be organized into groups according to their carbon skeletal structures. Alkaloid biosynthesis in plants involves many catalytic steps, catalyzed by enzymes that belong to a wide range of protein families. The characterization of novel alkaloid biosynthetic enzymes in terms of structural biochemistry, molecular and cell biology, and biotechnological applications has been the focus of research over the past several years. The application of genomics to the alkaloid field has accelerated the discovery of cDNAs encoding previously elusive biosynthetic enzymes. Other technologies, such as large-scale gene expression analyses and metabolic engineering approaches with transgenic plants, have provided new insights into the regulatory architecture of alkaloid metabolism.

Alteration of plant primary metabolism in response to insect herbivory

“…In contrast to carbohydrate transport, labeled nitrogen tracking studies have shown little evidence of jasmonic acid-induced nitrogen transport to elicited leaves in poplar (Arnold et al, 2004;Appel et al, 2012). Nevertheless, it is well established that defense-related nitrogenous compounds such as nicotine and other alkaloids are transported from roots to leaves upon insect attack (Baldwin et al, 1994;Hartmann and Ober, 2000;Ziegler and Facchini, 2008). Hence, it may be a common theme that plants deliver nitrogen as premanufactured resistance compounds but carbon as free carbohydrates for local production of defensive metabolites.…”

A Root-Expressed l-Phenylalanine:4-Hydroxyphenylpyruvate Aminotransferase Is Required for Tropane Alkaloid Biosynthesis in Atropa belladonna

“…One group of compounds, plant alkaloids, are widely used as stimulants, narcotics, and therapeutic agents and includes caffeine, nicotine, cocaine, morphine, scopolamine, vinblastine, and vincristine (Aniszewski, 2007;Grynkiewicz and Gadzikowska, 2008;Kingston, 2009). Alkaloids are a structurally heterogeneous family of ;12,000 compounds that are synthesized through diverse pathways and defined by the presence of a heterocyclic nitrogen atom (Ziegler and Facchini, 2008;O'Connor, 2010). The broad utility of alkaloids for humankind has led to considerable interest in understanding the pathways and regulatory mechanisms underlying their synthesis.…”

Tobacco nicotine uptake permease (NUP1) affects alkaloid metabolism

“…Plant tropane and monoterpenoid indole alkaloid biosynthesis are non-cell autonomous processes (27) requiring the efflux and uptake of alkaloid intermediates between different cell types. One apoplastic alkaloid uptake transporter has been characterized.…”