Orphan enzyme cuts down on sugar

The reclusive enzymes that catalyze proteolysis inside the cell membrane are among the most widespread in nature, yet most remain 'orphans' whose cellular functions are poorly understood. Now, Voss et al identify Golgi-resident glycosyltransferases and glycosidases as substrates for the presenilin-like protease SPPL3. Shedding of these glycan-modifying enzymes from the membrane down-regulates global protein N-glycosylation. The presenilin-like protease SPPL3 cleaves Golgi-resident glycosyltransferases and glycosidases to regulate global protein N-glycosylation.