The biosynthetic pathways of plantnaturalproducts offer an abundance of knowledge to scientists in many fields. Synthetic chemists can be inspired by the synthetic strategies that nature uses to construct these compounds. Chemical and biological engineers are working to reprogram these biosynthetic pathways to more efficiently produce valuable products. Finally, biochemists and enzymologists are interested in the detailed mechanisms of the complex transformations involved in the construction of these naturalproducts. Study of biosynthetic enzymes and pathways therefore has a wide-ranging impact. In recent years, many plant biosynthetic pathways have been characterized, particularly the pathways that are responsible for alkaloid biosynthesis. Here we highlight recently studied alkaloid biosynthetic enzymes that catalyze production of numerous complex medicinal compounds, as well as the specifier proteins in glucosinosolate biosynthesis, whose structure and mechanism of action are just beginning to be unraveled.