DUG2 (YBR281C, UniProt P38149) notes

• Identified in a screen for defective utilization of glutathione; GSH and gamma-Glu-Cys degradation "required the participation of the DUG2 and DUG3 gene products as well" PMID:17179087. "The DUG2 gene encodes a protein with a peptidase domain and a large WD40 repeat region" PMID:17179087.
• Cytoplasmic: "all three proteins were observed to have uniform GFP fluorescence throughout the cytoplasm" PMID:17179087.
• Biochemistry: "Dug2p, which has an N-terminal WD40 and a C-terminal M20A peptidase domain, has no peptidase activity." PMID:22277648; "purified Dug2p showed negligible cleavage of Cys-Gly peptide (only 4%)" PMID:22277648.
• "In vitro reconstitution assays revealed that Dug2p and Dug3p were required together for the cleavage of glutathione into glutamate and Cys-Gly." PMID:22277648; Dug2-Dug3 interaction via the Dug2 WD40 domain; Dug2 homodimerizes via its M20A domain; active complex (Dug2p-Dug3p)2, Km GSH 1.2 mM PMID:22277648.
• Catalytic nucleophile is the N-terminal Cys of Dug3 (GATase II) PMID:22277648; Dug2 is the non-catalytic (scaffold) partner.
• DUG2 and DUG3 derepressed by sulfur limitation PMID:22277648.

Annotation issues

• Peptidase/hydrolase/proteolysis IBA and IEA rows assume an active M20 dipeptidase; contradicted by direct assay. M20A predicted Zn ligands are annotated by similarity in UniProt but metal binding is unverified.
• Module (glutathione_synthesis_gamma_glutamyl_cycle) correctly models Dug2 as a non-catalytic partner of Dug3 in cytosol.
• YeastCyc: no Dug2/Dug3 reaction (glutathione + H2O -> glutamate + Cys-Gly) in PWYQT-4432 / PWY3O-114; only mentioned in the comment. The DUG pathway step is missing from YeastCyc.