Rapid high-resolution structure analysis of small, biotechnologically relevant enzymes by cryo-electron microscopy

ABSTRACT Enzyme catalysis has emerged as a key technology for developing efficient, sustainable processes in the chemical, biotechnological and pharmaceutical industries. Plants provide large and diverse pools of biosynthetic enzymes that facilitate complex reactions, such as the formation of intricate terpene carbon skeletons, with exquisite specificity. High-resolution structural analysis of these enzymes is crucial to understand their mechanisms and modulate their properties by targeted engineering. Although cryo-electron microscopy (cryo-EM) has revolutionized structural biology, its applicability to high-resolution structure analysis of comparatively small enzymes is so far largely unexplored. Here, we show that cryo-EM can reveal the structures of ~120 kDa plant borneol dehydrogenases at or below 2 Å resolution, paving the way for the fast development of new biocatalysts that provide access to bioactive terpenes and terpenoids.