paper : 05 metabolism of lipids module: 07 types of lipids iii
TRANSCRIPT
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
Paper : 05 Metabolism of Lipids
Module: 07 Types of Lipids III
Principal Investigator
Paper Coordinator and
Content Writer
Dr. Sunil Kumar Khare, Professor,
Department of Chemistry, IIT-Delhi
Dr. Suaib Luqman, Scientist (CSIR-CIMAP)
& Assistant Professor (AcSIR)
CSIR-CIMAP, Lucknow
Content Reviewer Prof. Prashant Mishra, Professor,
Department of Biochemical Engineering
and Biotechnology, IIT-Delhi
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
DESCRIPTION OF MODULE
Subject Name Biochemistry
Paper Name 05 Metabolism of Lipids
Module Name/Title 07 Types of Lipids III
Dr. Vijaya Khader Dr. MC Varadaraj
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
1. Objectives
To know about the complex lipids
What are the significance of glycolipids
How they act in a system
2. Concept Map
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
3. Description
3.1 Types of Lipids III
Complex Lipids
Glycolipids
In Mycobacteria LPS, Phosphatidylinositol dimannoside (lipoarabinomannan & lipomannan)
has been the anchoring domain and holds key significance in the interaction between host and
pathogen. This phosphatidylinositolglycans demonstrates the earliest version from prokaryotes
branded for cell surface protein anchoring and the lipoarabinomannan structural features have
been used across the globe as tuberculosis vaccine.
The surface of Leishmania, Entamoeba and Crithidia contains Lipophosphoglycan, a Glycolipid
serene with four domains: (1) an alkyl lyso phosphatidylinositol (2) core of glycan (3) Repeated
units of Gal-Man-PO4 backbone and (4) Cap structure of an oligosachharide has been involved
in a numerous functions inside the mammalian host.
In the strains of Streptococcus sp., Glucopyranosyl cardiolipin (Glycosylated cardiolipin) was
initially noticed and identified (18% of the lipid phosphorus) but present as a trifling constituent
in Vagococcus fluviatilis.
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
X = glucosyl residue
This infrequent glycolipid was also reported in Geobacillus steathermophilus (4% of total
phospholipids) acylated primarily by oleic acid (~ 25%) and palmitic acid (~ 33%). Revealed
predominantly as iso-C15:0 and anteiso-C17:0, this composite might be implicated in the
subvert effect of high temperature on the membrane organization and in the regulation of lipid
composition of G. stearothermophilus. In Deinococcus radiodurans, 3-(galactopyranosyl)-2-(3-
phosphatidyl) glyceroyl derivative, an exclusive glycophospholipid of a fatty alkylamine (~
33% of the total lipids) has also been identified.
The R3 (alkylamines) are generally straight chain compounds (C15-C17 or C16-C18), with
isomeric 17:1 bases preponderant.
A phosphocholine-containing glycoglycerolipid has been reported to be produced by
Mycoplasma fermentans in which the phosphocholine assembly is attached to the C6 of glucose
moiety. This lipid valor in the pathogenesis of rheumatoid arthritis by eliciting cell death or
inflammation through their phosphocholine dregs.
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
In Lactococcus and Streptococcus (Gram positive bacteria), a number of complex glycolipids
deriving from glucopyranosyl-1->2-glucopyranoside-diacylglycerol (kojibiosyl diacylglycerol
structure) were recognized.
(Acyl: fatty acyl group, Glcp: glycero-1-phospho, Ptd: 3-phosphatidyl)
In Staphylococcus membranes, additional complex phosphorylated compounds lipoteichoic
acids contains polymer of glycerol-1-phosphate allied to a glycosyl diglyceride or a
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
phosphatidyl glycosyl diglyceride is present. Other swapping on the glycerophosphate units
with alanyl or glycosyl groups has also been reported.
Structure of lipoteichoic acid from Bacillus subtilis where R1 and R2 are acyl group of fatty
acid and R3 is mainly acetylglucosaminyl, alanyl or H.
Sulfoglycoglycerolipids
Are lipids demeanoring a sulfur atom found in acidic membranes with a strong acidic pH (~2),
is present in some mammalian cells, chloroplast of higher plants, bacteria, algae and in fungi.
This type of lipid has also been described in Elakatothrix and Zygnema, green alga and in
Fucus, Pelvetia. At very low pH, carboxylic acids occur in unionized forms, but sulfolipids
subsist in the anionic form. In Chlorella, a new type of sulfolipid (sulfoquinovosyl
diacylglycerol: SQDG) derived from MGDG was discovered in 1959 at the Scripps Institute of
Oceanography (San Diego, CA, USA) which was afterward described in the thylakoid
membranes of all higher and lower plants. Hence, sulfolipids are present algae, cyanobacteria,
few basidiomycetes fungi (Clitocybe, Coprinus, Psalliota) and photosynthetic membranes of
plants,.
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
The biological function and mechanism for SQDG biosynthesis has been described in higher
plants predominantly under phosphate ravenous circumstances. SQDG is the lipid with a
sulfonic acid link, containing MGDG at C6 position of the monosaccharide unit,
sulfoquinovosyl (quinovose : 6-deoxy-D-glucose) is the sulfonoglucosidic moiety (6-desoxy-6-
sulfono-glucoside), R1 is often the palmitic acid and R2 is the unsaturated chain (16:3 n-3).
Heterosigma carterae (Raphidophyceae), a marine chloromonad was revealed to include a
intricate mixture of SQDG. The major fatty acyl groups contain 20:5 (n-3), 16:1 (n-3), 16:1 (n-
5), 16:1 (n-7) and 16:0. In Rhizobium meliloti, a symbiotic bacterium as well as in other strains
of Rhizobiaceae, existence of SQDG has been established. The occurrence of SQDG outside the
plant kingdom suggested the role of sulfolipid in the Rhizobium/legume relationship. In
Halobacterium, sulfate esters are reported with two alkyl diphytanylether chains. SQDG type
bearing mono-unsaturated (20:1 to 24:1) and saturated (14:0 to 24:0) fatty acids were also
extorted from a sea urchin (Scaphechinus mirabilis). Gustafson et al (1989) reported anti HIV-1
activity of SQDG from cyanobacteria containing linolenic and palmitic acids. Sulfate esters of
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
galactoglycerolipids are reported in quite a few mammalian tissues like brain, testis,
spermatozoa (3% of total lipids, >90% of total glycolipids in mammalian testis and ~0.3-1
mmole/g). The acyl groups R' and R'' are most frequently saturated (16/18 carbon atoms).
Seminolipids, mixture of alkylacyl and DAG is associated with myelination process of the
nervous system (Pieringer J et al., 1977, 166, 421). They are also essentail for mice
spermatogenesis. From Hyphomonas jannaschiana, a sea water bacterium, a tauroglycolipid has
been isolated lacking phospholipids. The structure determined as 1,2-diacyl-3-
glucuronopyranosyl-glycerol taurine-amide with 16:0, 16:1 n-7, 18:0, 18:1 n-7 and 19:0 as
major acyl chains.
i. Ceramides based Glycolipids:
Out of 150 known varieties in this cluster of glycosphingolipids, 50 categorized into the
structure of ganglio. Strewned mostly at the surface of the cell, they participate in the regulation
of cell interactions and dole out as distinctive markers for cells and mediate cell to cell detection
and contact. Ceramides based glycolipids are vital for the growth and development of organisms
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
and allude to viral or microbial infections and cancer. They form molecular complex named
‘Glycosynapse’ and helps in explicit recognition between cells function and signaling. They are
found in animals, bacteria, fungi, and plants. The grouping of glycosphingolipids is based on the
structure of the carbohydrate moiety and is as under:
Neutral glycosphingolipids (unsubstituted glycosyl group)
It includes single or extra glycosyl moieties, hexoses (sometimes pentose) and an added
hexosamine. As per the presence of glycosyl units they may be one glycosyl unit
(monoglycosylceramides), more than one glycosyl units (oligoglycosylceramidest) or
other structure containing only one glycosylated sphingoid base (deacylated
glycosphingolipids), one fatty acid linked to cerebrosides (acylated glycosphingolipids),
complex sphingolipids with a ceramide containing a cyclopropane chain and prenylated
residues on galactose (plakosides).
Acidic glycosphingolipids
Are zwitterionic molecules with glycosyl and carboxyl group, sulfate or phosphate.
Examples are gangliosides (a carboxyl group on sialic acid and several glysosyl
residues), acidic monoglycosylceramides, phosphonoglycosphingolipids,
sulfosphingolipids (ceramide di & tri hexosyl sulfate with one sulfate moeity on the
glycosyl unit, sulfatides), phosphosphingolipids (phosphorylceramide with
oligosaccharide or glycosyl head moeity).
ii. Lipopolysaccharides (LPS)
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Types of Lipids
Are the endotoxin (endotoxic-o-antigens) emanated from the cell walls of Gram negative
bacteria and in a fungus (Antrodia camphorata). Due to their nature, they may cause numerous
pathophysiological symptoms like blood pressure decrease, diarrhea, fever, septic shock and
death. There are three parts in LPS, part A (Lipid A) silhouette a composite with part B
(polysaccharide core) through a glycosidic linkage which is allied to an external area of part C
(an immunogenic and capricious polysaccharide chain or antigen composed up of repeating
oligosaccharide units liable for the specificity of bacterial serological strain. Part A (Lipid A)
includes a backbone of b 1, 6-glucosaminylglucosamine with two phosphoester moiety at
position 1 of glucosamine I and in position 4 of glucosamine II. The position 3 of glucosamine
II assembles the glycosidic linkage (acid labile) to the polysaccharide chain. In E. coli, the
supplementary groups are replaced with fatty acids ((hydroxylated) as hydroxymyristate (two
amide & two ester linked) and laurate (fatty acid). In the same species, the LPS fatty acid
profiles vary distinctly from the phospholipids.
Structure of lipid A of Escherichia coli
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
3-hydroxyalkanoic acids and 2-hydroxyalkanoic acids are common hydroxylated fatty acids but
some bacteria (Achromobacter, Bacteroides, Brucella, Gardnerella, Sorangium, Thermus,
Thiobacillus) lacks hydroxy acids. Even carbon compounds (12-18 atoms) containing hydroxy
acids are straight-chain while odd-carbon acids are minor components (13-17 atoms) of
Bordetella, Pseudomonads, Pectinatus, Selenomonas, Vibrio and Veillonella. In
Capnocytophaga, Flavobacterium, Desulfovibrio, Legionella, Pseudomonas and Moraxella,
species a specialized branched chain hydroxy fatty acids (3OH i 11:0 up to3OH i 17:0) has also
been reported. In Pseudomonas and Azospirillum species, a small number of unsaturated
hydroxy fatty acids have been depicted, except the presence of 2OH, 18:1.
Listeria monocytogenes, an infective agent in milk, is the solitary Gram positive bacteria that
acquire LPS where the polysaccharide is non-toxic and the toxic activity is attributed to the part
A (Lipid A) that causes septic shock. The subsistence of LPS was established in a fungus
(Antrodia camphorate) of Polyporaceae family revealing fucose, glucose, galactose and sorbitol
in LPS, galactosamine and glucosamine were deficient. Furthermore, the sequestered compound
showed some anti-inflammatory effect and a low cytotoxicity. An efficient method using hot
ammonium isobutyrate solvent for the extraction of LPS and sequestration of lipid A from
bacteria has been described. Lipid X a closely related precursor of lipid A has also been
portrayed revealing various pharmacological properties.
iv. Sterol based Glycolipids:
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
They occur as free sterols, esters (acylated), alkyl ethers (alkylated), sulfated or linked to a
steryl glycoside moiety. The biosynthesis of sterol is everpresent amid eukaryotes but almost
wholly deficient in prokaryotes. Being absent in Archaea, they are sparingly distributed in
bacteria and Methylococcus capsulatus (proteobacterium), Gemmata obscuriglobus
(planctomycete) along with myxobacteria members. As a consequence, the existence of varied
steranes (saturated 4 cycle skeleton) in primordial rocks is used as proof for eukaryotic
evolution somewhere 2.7 billion years ago.
Structure of sterols with carbon numbers
The sterols have hopanoids as precursor and an oxygen-dependent biosynthesis starting with the
creation of 2, 3-oxidosqualene (primary intermediate). Hence, steroid and triterpenoid
hydrocarbon detection in the history of Earth has been used to surmise the relic of oxygenic
photosynthesis. It has been conjecture that levels of oxygen increased in the atmosphere made
the sterols evolution feasible and make possible the eukaryotes birth giving them with an
untimely protection mechanism against oxygen.
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Biochemistry METABOLISM OF LIPIDS
Types of Lipids
Free Sterols
Sterols (Greek: stereos-solid) shape an imperative cluster amid steroids. The unsaturated
steroids involve a 3-hydroxyl group (cholestane skeleton) and carbon atoms (8 or more) of an
aliphatic side chain at position 17 figuring the group of sterols. Being saponification resistant,
they are endowed in all animal and vegetal tissues important in the appraisal of marine sediment
maturity as a biological marker compound, yet past hundreds millions years. They also
comprise 3-hydroxysteroids (C27 to C30) crystalline alcohols and are classed as triterpenes
(being derived from squalene) directly by unsaturation, cyclization and 3-hydroxylation,
cycloartenol in plants or lanosterol in animals.
5cholestane
4. Summary
In this lecture we learnt about:
The Types of Glycolipids
Their benefit & advantages