B12 Enzyme, Volume 667 in the Methods in Enzymology serial, highlights new advances in the field with this new volume presenting timely, interesting chapters, including Part I: B12 Biosynthesis and B12 Chaperones, Probing the preference and regioselectivity of lower ligand activation and its role in cobamide diversity, Biosynthesis of corrinoids, The human B12 trafficking chaperones: CblC, CblD and ATR, A method for the efficient adenosylation of corrinoids, Production, purification and liposome reconstitution of cobamide synthase, Extraction and Purification of Cobamides from Bacterial Cultures, Part II: The many faces of B12-dependent enzyme reactions, Methylcobalamin-dependent methionine synthase, and much more.