Alkaloid biosynthesis is the genetically encoded, enzyme-mediated formation of alkaloids: nitrogen-containing natural products produced through specialized metabolic pathways. It encompasses the conversion of central-metabolic precursors into alkaloid core structures and the subsequent reactions that generate structurally distinct alkaloid products. Alkaloid-producing bacteria, fungi, and plants possess different pathway architectures and enzyme repertoires; consequently, alkaloid classes do not necessarily share a single precursor, sequence of intermediates, or biosynthetic mechanism ^[1]. In established plant pathways, amino acids and their derivatives commonly provide carbon and nitrogen inputs for the formation of alkaloid frameworks ^[2]. Biosynthesis includes scaffold-forming transformations and downstream tailoring reactions, such as oxidation, reduction, methylation, acylation, and glycosylation, which alter the molecular structure of pathway intermediates ^[1][3]. The term denotes endogenous biological production and its associated enzymes and genes; it excludes laboratory chemical synthesis, semisynthesis, extraction, isolation, and structural analysis of alkaloids.