Abstract

Monoglyceride lipases (MGLs) are a group of α/β-hydrolases that catalyze the hydrolysis of monoglycerides (MGs) into free fatty acids and glycerol. This reaction serves different physiological functions, namely in the last step of phospholipid and triglyceride degradation, in mammalian endocannabinoid and arachidonic acid metabolism, and in detoxification processes in microbes. Previous crystal structures of MGLs from humans and bacteria revealed conformational plasticity in the cap region of this protein and gave insight into substrate binding. In this study, we present the structure of a MGL from Saccharomyces cerevisiae called Yju3p in its free form and in complex with a covalently bound substrate analog mimicking the tetrahedral intermediate of MG hydrolysis. These structures reveal a high conservation of the overall shape of the MGL cap region and also provide evidence for conformational changes in the cap of Yju3p. The complex structure reveals that, despite the high structural similarity, Yju3p seems to have an additional opening to the substrate binding pocket at a different position compared to human and bacterial MGL. Substrate specificities towards MGs with saturated and unsaturated alkyl chains of different lengths were tested and revealed highest activity towards MG containing a C18:1 fatty acid.

Highlights

  • Lipases are hydrolases that cleave ester bonds in lipids and act at a water–lipid interface

  • Monoglyceride lipases (MGLs) are a group of α/β-hydrolases that catalyze the hydrolysis of monoglycerides (MGs) into free fatty acids and glycerol

  • We present the structure of a MGL from Saccharomyces cerevisiae called Yju3p in its free form and in complex with a covalently bound substrate analog mimicking the tetrahedral intermediate of MG hydrolysis

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Summary

Introduction

Lipases are hydrolases that cleave ester bonds in lipids and act at a water–lipid interface. Many lipases contain a variable lid or cap region which covers the active site and forms the substrate binding pocket in combination with an α/β-hydrolase core domain. In some lipases, this cap region is considered to play a role in interfacial activation [1,2]. Enzymes involved in degradation of these lipid depots may be essential in providing energy and precursors for cell wall synthesis during the reactivation step and the chronic phase [18] Due to these different biological roles, MGLs are interesting subjects for drug targeting [14,18,19,20].

Experimental methods
Cloning and mutagenesis of s-Yju3p
Monoglyceride hydrolase activity assay
Data processing and structure refinement: s-Yju3p
Data processing and structure refinement: s-Yju3p substrate analog complex
Heavy metal soaking and MAD data collection
Results and discussion
Conformational flexibility in the cap of s-Yju3p
Cavity shape and substrate binding versus substrate selectivity
Full Text
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