Terpenoid natural products comprise the largest and most structurally diverse class of natural products observed to date. These complex secondary metabolites are synthesized in all domains of life, exhibit potent bioactivities, and are critically important compounds in a number of chemical industries, including the pharmaceutical, energy, and cosmetic industries. Despite the remarkable diversity observed among this class of natural products, all terpenes derive from a mere handful of common primary metabolites, collectively known as isoprenoid diphosphates. Specialized enzymes of secondary metabolism (e.g.; terpenoid cyclases or aromatic prenyltransferases) use these common substrates to generate the diverse hydrocarbon scaffolds that underlie over 102,000 terpenoid natural products. Crystallographic and biochemical studies which illuminate the structure-function relationships of these enzymes help to unravel the complex molecular basis of catalysis. Understanding the structures and chemical mechanisms of biosynthetic enzymes is a crucial step in guiding structure-based engineering approaches to generate new and useful synthetic biology tools. This thesis examines the structural and chemical biology of two microbial terpenoid biosynthetic enzymes, epi-Isozizaene Synthase and Reverse N-Dimethylallyl-L-Tryptophan Synthase 1.