The Enzymes, Volume 54 highlights new advances in enzymes, with new chapters on a variety of topics, including the History of The Enzymes, Impact of The Enzymes in chronicling biochemical processes and pathways, Metabolism and Catalysis, Mitochondrial ATP synthase, The respiratory chain, A century of mitochondrial research, Five decades of metalloenzymology, Mechanisms of catalysis, Mitochondrial fatty acid synthesis and associated processes, Signaling, MAPK cascades: Origins, mechanisms and current status, Sphingolipids: From structural components to signaling hubs, Protein Homeostasis and Hydrolysis, Mitochondrial AAA+ proteases, Hsp70 and JDP proteins: structure-function perspective on molecular chaperone activity. Other sections cover DNA Replication and Repair, Structure-function studies of DNA replication proteins, and Helicases required for nucleotide excision repair.