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Enzyme
Compound
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Target Concepts:
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Query: UMLS:C1832526 (
PCC
)
5,967
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Heterocysts are the specialized cells for nitrogen fixation in some filamentous cyanobacteria. To protect the oxygen labile nitrogen fixing enzyme, nitrogenase, heterocysts keep their inner environment microoxic by developing layers of barrier on the outside of their outer membranes. Heterocyst specific glycolipids (Hgls) are constituents of the layer of barrier and amphipathic compounds, synthesized from a very
long chain
fatty alcohol as a hydrophobic tail and a sugar as a polar head. In the model heterocystous cyanobacterium Anabaena sp.
PCC
7120, Hgls are made of fatty alcohol with 26 carbons and a glucose, linked by an ether bond in alpha configuration. The fatty alcohol is synthesized via reactions of a polyketide synthase, HglE
A
. In Anabaena sp.
PCC
7120, another polyketide synthase HglE2 shared more than 50% identity in an amino acid sequence with HglE
A
and is expected to be involved in Hgls synthesis. However, no direct evidence has been reported. Here, we experimentally show that HglE
A
is the contributor of Hgls synthesis, and that HglE2 is not involved in the development of the heterocyst specific glycolipid layer.
...
PMID:A polyketide synthase HglE
A
, but not HglE2, synthesizes heterocyst specific glycolipids in Anabaena sp. PCC 7120. 3207 20
The heterocysts present in filamentous cyanobacteria such as
Anabaena
sp.
PCC
7120 are known to be regulated by HetN and PatS, the repressors of heterocyst differentiation; therefore, the inactivation of these proteins will result in the formation of multiple heterocysts. To enhance the accumulation of fatty alcohols synthesized in the heterocyst, we introduced mutations of these repressors to increase heterocyst frequency. First, we isolated double mutants of
hetN
and
patS
and confirmed that the null mutation of these genes promoted higher frequencies of heterocyst formation and higher accumulation of heterocyst-specific glycolipids (Hgls) compared with its wild type. Next, we combined
hetN
and
patS
mutations with an
hglT
(encoding glycosyltransferase, an enzyme involved in Hgl synthesis) mutation to increase the accumulation of fatty alcohols since knockout mutation of
hglT
results in accumulation of very
long chain
fatty alcohol, the precursor of Hgl. We also observed retarded growth, lower chlorophyll content and up to a five-fold decrease in photosynthetic activity of the
hetN
/
patS
/
hglT
triple mutants. In contrast, the triple mutants showed three times higher heterocyst formation frequencies than the
hglT
single mutant and wild type. The production rate of fatty alcohol in the triple mutants attained a value 1.41 nmol/mL OD
730
, whereas accumulation of Hgls in the wild type was 0.90 nmol/mL OD
730
. Aeration of culture improved the accumulation of fatty alcohols in
hetN
/
patS
/
hglT
mutant cells up to 2.97 nmol/mL OD
730
compared with cells cultured by rotation. Our study outlines an alternative strategy for fatty alcohol production supported by photosynthesis and nitrogen fixation.
...
PMID:
hetN
and
patS
Mutations Enhance Accumulation of Fatty Alcohols in the
hglT
Mutants of
Anabaena
sp. PCC 7120. 3273 94
