SAC1 (P32368, YKL212W) notes

Evidence journal (YeastPathways phosphoinositide_biosynthesis batch, 2026-10-06).

Activity

• Phosphoinositide phosphatase; PtdIns3P and PtdIns4P hydrolysis, low activity on PtdIns(3,5)P2 [UniProt:P32368 "Has low activity towards phosphatidylinositol-3,5-"].
• PMID:10625610; sac1 mutants alter PtdIns4P and PI(4,5)P2 levels.
• Principal in vivo substrate PtdIns4P PMID:11514624; mainly the Stt4 pool PMID:11514624.
• PMID:11792713; Osh-stimulated activity PMID:21295699.

YeastPathways assignments

• PI4P -> PI (EC 3.1.3.-): correct, core.
• PI3P -> PI (EC 3.1.3.64): supported in vitro; ER PI3P pool PMID:11792713. Physiological PI3P phosphatases are mainly Ymr1/Sjl2/Sjl3.
• PI(3,5)P2 dephosphorylation mapped to GO:0043813 (5-phosphatase): questionable - Sac1 activity on PI(3,5)P2 is low and SGD curated it as 3-phosphatase (GO:0052629); Fig4 is the physiological 5-phosphatase. Marked over-annotated; the derived IEA 'PI3P biosynthetic process' removed.
• RCA 'phosphatidylinositol phosphate biosynthetic process' is the wrong direction for a phosphatase -> MODIFY to PI dephosphorylation.

Location

• ER membrane, type II TM PMID:11792713; Golgi on growth arrest PMID:15657391; cortical ER PMID:30785834; medial Golgi via Vps74 PMID:22553352.
• Mitochondrial proteome hits treated as contamination.

Other

• SPOTS complex member PMID:20182505.
• Autophagosome-vacuole fusion PMID:32693712.
• Co-opted by TBSV (PMID:32269127).