8.A.187. The Lipase Atg15 (Atg15) Family
Autophagy (see TC families 9.A.15, 9.B.26 and 9.B.134) is a cellular degradation process widely conserved among eukaryotes. During autophagy, cytoplasmic materials fated for degradation are compartmentalized in double membrane-bound organelles called autophagosomes. After fusing with the vacuole, their inner membrane-bound structures are released into the vacuolar lumen to become autophagic bodies and eventually degraded by vacuolar hydrolases. Atg15 is a lipase that is essential for disintegration of autophagic body membranes and has a transmembrane domain at the N-terminus and a lipase domain at the C-terminus. Hirata et al. 2021 found that the N-terminal domain alone can travel to the vacuole via the multivesicular body pathway, and that targeting of the C-terminal lipase domain to the vacuole is required for degradation of autophagic bodies. Moreover, the C-terminal domain could disintegrate autophagic bodies when it was transported to the vacuole via the Pho8 pathway instead of the multivesicular body pathway. H435 is one of the residues composing the putative catalytic triad, and W466 is an important residue for degradation of autophagic bodies. Thus, the C-terminal lipase domain recognizes autophagic bodies to degrade them (Hirata et al. 2021).
Atg15 lipase, AUT5 or CVT17, of 520 aas and kone N-terminal TMS, catalyzes the hydrolysis of triacylglycerides to a fatty acid and a diacylglyceride. See the family description for an explanation of its function.
Atg15 of Saccharomyces cerevisiae
Uncharacterized protein (probable lipase) of 456 aas and one N-terminal TMS.
Putative lipase of Paenibacillus polymyxa
Uncharacterized protein of 245 aas and one N-terminal TMS.
UP of Chromatiales bacterium (ex Bugula neritina AB1)
Unharacterized protein of 343 aas and 1 N-terminal TMS.
UP of Floricoccus penangensis
Uncharacterized protein of 1090 aas and ~13 TMSs in a 2 + 2 + 2 + 3 + 1 + 3 TMS arrangement. Only the C-terminal region (residues 855 - 1035) show similarity with other members of this family.
UP of Piromyces sp. E2
Uncharacterized protein of 326 aas and possibly one central TMS.
UP of Candidatus Gastranaerophilales bacterium HUM_15 (human gut metagenome)
Uncharacterized protein of 342 aas and one N-terminal TMS plus a possible central TMS.
UP of Marchantia paleacea
Uncharacterized protein of 906 aas and possibly 9 TMSs in a 2 + 2 + 5 TMS arrangement.
UP of Thecamonas trahens