The cell membrane of Mycoplasma penetrans: lipid composition and phospholipase A1 activity

https://doi.org/10.1016/0005-2736(95)80026-CGet rights and content
Under an Elsevier user license
open archive

Abstract

Analysis of Mycoplasma penetrans membrane lipids revealed that, in addition to large amounts of unesterified cholesterol, M. penetrans incorporated exogenous phospholipids, preferentially sphingomyelin, from the growth medium. The major phospholipids synthesized de novo by M. penetrans were phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG). In vivo labeling of PG and DPG by growing the cells with radioactive palmitate or oleate, followed by snake venom phospholipase A2 treatment, enabled us to assess the positional distribution of fatty acids in these lipids. Saturated fatty acids were found preferentially in position 2 of the glycerol backbone, and not in position 1 as found elsewhere in nature, while unsaturated fatty acids prefer position 1. M. penetrans membranes contain phospholipase activity of the A1 type, removing a fatty acid from the sn-1 ester bond of phospholipids. The activity was neither stimulated by Ca2+ nor inhibited by EGTA and had a broad pH spectrum. The substrate specificity of the enzyme was investigated with various natural lipids and with a fluorescent analog of the phosphatidylcholine. The enzyme was equally active toward phosphatidyl-choline and phosphatidylglycerol, but did not hydrolyze diphosphatidylglycerol. The enzyme did not act on triacylglycerol, diacylglycerol or cholesteryl ester, but low activity was detected toward monoacylglycerol. The enzyme was heat-sensitive and detergent-sensitive, and was almost completely inhibited by p-bromophenacylbromide (50 μM), but was not affected by SH reagents. This study is the first one reporting phospholipase A1 activity in Mollicutes. A possible role of this enzyme in forming lipid mediators upon the interaction of M. penetrans cells with eukaryotic cells is suggested.

Keywords

Phospholipase A1
Membrane lipid
AIDS
(Molliicutes)
(Mycoplasma penetrans)

Abbreviations

SPM
sphingomyelin
PC
phosphatidylcholine
PG
phosphatidylglycerol
DPG
diphosphatidylglycerol
C6-NBD-PC
1-acyl-2-(6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)]aminocaproyl)phosphatidyl-choline
NBD-PE
N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)diacylphospha-tidylethanolamine
C6-NBD-DAG
C6-NBD-diacylglycerol
C6-NBD-PA
C6-NBD-phosphatidic acid
C6-NBD-FA
NBD-caproic acid
C6-NBD-LPC
C6-NBD-lyso-PC
DTNB
dithiobis(2-nitrobenzoic acid)
PBP
p-bromophenacylbromide
DTT
dithiothreitol
PLA1
phospholipasc A1
PLA2
phospholipasc A2
NEM
N-ethylmaleimide
FFA
free fatty acid

Cited by (0)