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ZUFSP-type enzymes cleave ubiquitin chains in a linkage-specific fashion, but members from different organisms have different specificities. Using an inter-kingdom comparison of activities and structures, the authors identify the domains responsible for this discrepancy.

Mutations in the hexosamine pathway key enzyme glutamine fructose-6-phosphate amidotransferase (GFAT-1) improve protein quality control and extend C. elegans lifespan. Here the authors present the crystal structures of full-length human GFAT-1 alone and with bound ligands and perform activity assays, which show that gain-of-function in the longevity-associated G451E variant is caused by a loss of feedback regulation.

Deubiquitinating enzymes (DUBs) are essential to modulate ubiquitin signaling. While known DUBs can be grouped into six families, the authors here present biochemical and structural evidence for a seventh DUB family, defining determinants of substrate specificity for two representative enzymes.