Journal of Lipid Research, Vol 35, 1932-1945, Copyright © 1994 by Lipid Research, Inc.
Structures and stereochemistry of the very long alpha, omega- bifunctional alkyl species in the membrane of Sarcina ventriculi indicate that they are formed by tail-to-tail coupling of normal fatty acids
S Jung and RI Hollingsworth
Department of Biochemistry, Michigan State University, East Lansing 48824.
In a previous study, we demonstrated that Sarcina ventriculi is capable of
adjusting to alterations in environmental conditions (such as increase in
temperature, lowering of pH, or addition of exogenous organic solvents) by
the synthesis of a family of alpha, omega- dicarboxylic acids ranging from
28 to 36 carbons long (Jung, S., et al. 1993. J. Biol. Chem. 268:
2828-2835). The chain lengths and relative abundance of the very long
dicarboxylic acids found in S. ventriculi suggest that they may be formed
after the perturbation by the (enzymatic) tail-to-tail combinations of
existing regular monofunctional fatty acids and not completely de novo by
direct 2- carbon addition of acetyl coenzyme A (CoA). If this were true,
knowing the structures of the regular fatty acids, we can predict those of
the very long chain bifunctional acids. In this work we present definitive
chemical results that strongly support this mechanism. This was done by
analyzing the structures and stereochemistry of the very long bifunctional
species in the light of those of the regular monofunctional species. The
exact structures of membrane fatty acid methyl ester derivatives components
were determined by various spectroscopic and chemical methods including gas
chromatographic (GC) analysis, gas chromatography-mass spectrometry
(GC-MS), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier
transform infrared (FTIR) spectroscopy, polarimetry, and reductive
ozonolysis. This yielded precise structural and stereochemical information
on the position of substitution of the acyl chain by methyl groups,
position and configuration of double bonds, and optical activity. These
results, coupled with the absence of intermediate length acyl species,
indicated that the very long alkyl species (without exception) can be
formed by tail-to-tail joining of existing fatty acids. The ideas of a
dynamically regulated catalytic system is proposed.
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