Identification of New Sphingomyelinases D in Pathogenic Fungi and Other Pathogenic Organisms

Camila Dias-Lopes,Carlos Chávez-Olortegui,José Miguel Ortega,Franck Molina,Liza Felicori,Izabella A P Neshich,Goran Neshich,Claude Granier,Eugene A Permyakov

doi:10.1371/journal.pone.0079240

Abstract

Sphingomyelinases D (SMases D) or dermonecrotic toxins are well characterized in Loxosceles spider venoms and have been described in some strains of pathogenic microorganisms, such as Corynebacterium sp. After spider bites, the SMase D molecules cause skin necrosis and occasional severe systemic manifestations, such as acute renal failure. In this paper, we identified new SMase D amino acid sequences from various organisms belonging to 24 distinct genera, of which, 19 are new. These SMases D share a conserved active site and a C-terminal motif. We suggest that the C-terminal tail is responsible for stabilizing the entire internal structure of the SMase D Tim barrel and that it can be considered an SMase D hallmark in combination with the amino acid residues from the active site. Most of these enzyme sequences were discovered from fungi and the SMase D activity was experimentally confirmed in the fungus Aspergillus flavus. Because most of these novel SMases D are from organisms that are endowed with pathogenic properties similar to those evoked by these enzymes alone, they might be associated with their pathogenic mechanisms.

Highlights

Sphingomyelinases D (SMases D; EC 3.1.4.41), known as sphingomyelin phosphodieasterases D and sometimes as phospholipase D (PLD) [1], catalyze the hydrolytic cleavage of sphingomyelin or many other lysophospholipids to produce choline and ceramide 1-phosphate or choline and lysophosphatidic acid (LPA), respectively [2,3]
Intrigued by the presence of this toxic enzyme in medically important but distantly related organisms, such as spiders and bacteria, Cordes and Binford [12] identified a common motif at the C-terminal end of SMase D, supporting their inference about the origins of these enzymes from the broadly conserved glycerophosphoryl diester phosphodiesterase (GDPD; EC 3.1.4.46) family, in which, this motif is absent
The protein sequences found as hits were used as queries in a BLASTp search against a test set database containing only the true positive (SMases D from Corynebacterium, Loxosceles and Ixodes) and true negative sequences – both recovered from the BRENDA databank [14]

Summary

Introduction

Sphingomyelinases D (SMases D; EC 3.1.4.41), known as sphingomyelin phosphodieasterases D and sometimes as phospholipase D (PLD) [1], catalyze the hydrolytic cleavage of sphingomyelin or many other lysophospholipids to produce choline and ceramide 1-phosphate or choline and lysophosphatidic acid (LPA), respectively [2,3] These enzymes are found in the venom of spiders from the Sicariidae family and are responsible for the outcome of local dermonecrosis in victims that suffer spider bites, as well as the systemic toxic effects, such as kidney failure and death [4,5,6,7,8]. This work suggests that SMases D are widely represented in several genera and may act as a common pathogenic effector for a significant diversity of organisms

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Conclusion