A new mechanism for anaerobic unsaturated fatty acid formation in Streptococcus pneumoniae

The anaerobic pathway for unsaturated fatty acid synthesis was established in the 1960s in Escherichia coli. The double bond is introduced into the growing acyl chain by FabA, an enzyme capable of both the dehydration of beta-hydroxydecanoyl-acyl carrier protein (ACP) to trans-2-decenoyl-ACP, and th...

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Bibliographic Details
Published in:The Journal of biological chemistry 2002-11, Vol.277 (47), p.44809-44816
Main Authors: Marrakchi, Hedia, Choi, Keum-Hwa, Rock, Charles O
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Anaerobiosis
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - isolation & purification
Bacterial Proteins - metabolism
Carrier Proteins - metabolism
Escherichia coli - metabolism
Fatty Acids, Unsaturated - biosynthesis
Genetic Complementation Test
Hydro-Lyases - chemistry
Hydro-Lyases - genetics
Hydro-Lyases - isolation & purification
Hydro-Lyases - metabolism
Isomerases - chemistry
Isomerases - genetics
Isomerases - isolation & purification
Isomerases - metabolism
Molecular Sequence Data
Molecular Weight
Multigene Family
Oxygen - metabolism
Sequence Alignment
Spectrometry, Mass, Electrospray Ionization
Streptococcus pneumoniae - genetics
Streptococcus pneumoniae - metabolism
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Summary:The anaerobic pathway for unsaturated fatty acid synthesis was established in the 1960s in Escherichia coli. The double bond is introduced into the growing acyl chain by FabA, an enzyme capable of both the dehydration of beta-hydroxydecanoyl-acyl carrier protein (ACP) to trans-2-decenoyl-ACP, and the isomerization of trans-2 to cis-3-decenoyl-ACP. However, there are a number of anaerobic bacteria whose genomes do not contain a fabA homolog, although these organisms nonetheless produce unsaturated fatty acids. We cloned and biochemically characterized a new enzyme in type II fatty acid synthesis from Streptococcus pneumoniae that carries out the isomerization of trans-2-decenoyl-ACP to cis-3-decenoyl-ACP, but is not capable of catalyzing the dehydration of beta-hydroxy intermediates. This tetrameric enzyme, designated FabM, has no similarity to FabA, but rather is a member of the hydratase/isomerase superfamily. Thus, the branch point in the biosynthesis of unsaturated fatty acids in S. pneumoniae occurs following the formation of trans-2-decenoyl-ACP, in contrast to E. coli where the branch point takes place after the formation of beta-hydroxydecanoyl-ACP.
ISSN:0021-9258
DOI:10.1074/jbc.M208920200