AADACL2

Model summary

A human ER-associated serine hydrolase that adopts an α/β-hydrolase scaffold and a lipase-like GDXG catalytic core to hydrolyze acyl-ester and related substrates. By forming a catalytic acyl-enzyme intermediate via a nucleophilic serine, it contributes broadly to xenobiotic detoxification and neutral-lipid turnover at the membrane interface. Its activity supports the breakdown of acylated drugs and endogenous lipids within the endoplasmic reticulum membrane environment, coordinating with local detoxification and lipid-handling pathways.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The polypeptide is dominated by IPR029058 (Alpha/Beta hydrolase fold homologous superfamily, residues 58–401), establishing a classical α/β-hydrolase scaffold that supports a catalytic triad and oxyanion stabilization. Within this scaffold, two internal modules—IPR013094 (Alpha/beta hydrolase fold-3 domain, residues 107–258) and IPR013094 (Alpha/beta hydrolase fold-3 domain, residues 311–373)—partition the core fold into subdomains that position the nucleophile and general base. The enzyme is assigned to IPR017157 (Arylacetamide deacetylase family, residues 3–401), a clade of carboxylester/amide-deacetylating enzymes that act on xenobiotic and endogenous acyl esters. IPR050300 (GDXG lipolytic enzyme family, residues 73–400) specifies a lipolytic chemistry driven by a conserved G–D–X–G motif that organizes the catalytic apparatus. Critically, IPR033140 (Lipase, GDXG, putative serine active site, residues 183–195) marks the nucleophilic serine that, together with the canonical acidic and histidine residues of the α/β-hydrolase fold, forms the charge-relay system. The ordered layout—broad α/β-hydrolase core, embedded lipase-specific modules, and a defined serine nucleophile—causally dictates serine hydrolase chemistry and lipase-class reactivity.

2. 02

   This architecture enforces molecular functions that hinge on a serine-dependent hydrolytic mechanism.

   The nucleophilic serine and oxyanion hole confer GO:0017171 serine hydrolase activity. The lipolytic family signature and α/β-hydrolase fold-3 modules support GO:0004806 triglyceride lipase activity, as this fold commonly catalyzes acyl-ester cleavage in neutral-lipid contexts. In this protein, the arylacetamide deacetylase family membership and lipase-like GDXG motif extend substrate scope to diverse acyl esters and amides, aligning with broad detoxification and lipid-modulating chemistries.

3. 03

   From these molecular activities, the biological role follows.

   A serine hydrolase of the arylacetamide deacetylase family typically participates in xenobiotic handling by hydrolyzing acylated drugs and environmental chemicals, funneling them toward excretable acids and alcohols. This causally links the enzyme to GO:0006805 xenobiotic metabolic process. The lipase-like capacity further suggests roles in lipid remodeling and signaling, but the xenobiotic focus is reinforced by the family identity and membrane-proximal context.

4. 04

   Cellular placement is inferred from the absence of soluble targeting signals and the functional coupling to membrane-associated detoxification pathways.

   The α/β-hydrolase scaffold often operates at membrane interfaces, and xenobiotic metabolism in human cells is frequently organized at the endoplasmic reticulum. The most parsimonious localization is GO:0005789 endoplasmic reticulum membrane, where the enzyme can access hydrophobic substrates emerging from membrane bilayers and coordinate with ER-resident detoxification machinery.

5. 05

   Mechanistically, the enzyme likely uses a catalytic triad centered on the GDXG-marked serine (183–195) to form and resolve an acyl-enzyme intermediate.

   The ER membrane setting concentrates hydrophobic xenobiotics and lipid substrates; the enzyme’s lipase-like fold and serine chemistry enable broad acyl-ester turnover. I hypothesize transient assemblies with ER-resident detoxification and lipid-handling modules—such as cytochrome P450 systems and lipid-transfer or scaffolding proteins—to channel substrates and products efficiently. This cooperative interface would allow the enzyme to hydrolyze acylated xenobiotics and neutral-lipid esters while modulating ER-localized metabolic fluxes.