Cooperative enzymatic control of N-acyl amino acids by PM20D1 and FAAH.

Joon T Kim,Stephanie M Terrell,Curt R Fischer,Veronica L Li,Jonathan Z Long,Wei Wei

doi:10.7554/elife.55211

Abstract

The N-acyl amino acids are a family of bioactive lipids with pleiotropic physiologic functions, including in energy homeostasis. Their endogenous levels are regulated by an extracellular mammalian N-acyl amino acid synthase/hydrolase called PM20D1 (peptidase M20 domain containing 1). Using an activity-guided biochemical approach, we report the molecular identification of fatty acid amide hydrolase (FAAH) as a second intracellular N-acyl amino acid synthase/hydrolase. In vitro, FAAH exhibits a more restricted substrate scope compared to PM20D1. In mice, genetic ablation or selective pharmacological inhibition of FAAH bidirectionally dysregulates intracellular, but not circulating, N-acyl amino acids. Dual blockade of both PM20D1 and FAAH reveals a dramatic and non-additive biochemical engagement of these two enzymatic pathways. These data establish FAAH as a second intracellular pathway for N-acyl amino acid metabolism and underscore enzymatic division of labor as an enabling strategy for the regulation of a structurally diverse bioactive lipid family.

Highlights

The N-acyl amino acids are a large family of bioactive lipids composed of a fatty-acid tail conjugated to an amino acid head group
We identify the responsible enzyme as fatty acid amide hydrolase (FAAH) and establish how PM20D1 and FAAH engage in extensive non-additive interactions in vivo to regulate the levels of N-acyl amino acids cooperatively
The second PM20D1-independent activity accounted for 70% and 11% of the total C20:4-Gly hydrolysis in brain and liver, respectively

Summary

Introduction

The N-acyl amino acids are a large family of bioactive lipids composed of a fatty-acid tail conjugated to an amino acid head group. We have recently identified a new role for certain N-acyl amino acids in stimulating oxidative metabolism via mitochondrial uncoupling (Long et al, 2016) These thermogenic N-acyl amino acids are characterized by medium-chain fatty acyl chains and neutral amino acid head groups, chemical features that are present in a subset of family members including N-acyl phenylalanines, N-acyl leucines, N-acyl glycines, and N-acyl serines (Keipert et al, 2017; Lin et al, 2018). Administration of these N-acyl amino acids to mice rendered obese by feeding a high-fat diet increases energy expenditure, reduces adiposity, and improves glucose homeostasis

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