Chlorophyll is a green pigment essential for photosynthesis. It was first isolated in 1817 and its chemical structure was determined in 1940. Chlorophyll molecules contain a porphyrin group with a magnesium ion at the center and a phytol tail. Chlorophyll absorbs blue and red light, reflecting green light, giving plants their green color. Its biosynthesis involves multi-step pathways producing intermediates like protoporphyrin IX and geranylgeranyl diphosphate, which are then combined to form chlorophyll. The process takes place via membrane-bound enzymes in the chloroplast and results in the insertion of magnesium and addition of the phytol tail to the chlorophyll molecule.

1. Biosynthesis and Properties of chlorophyll
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representing
the title of
the Topic
By Shariqa Aisha
University of Kashmir
Department of
Bioresources

2.  Introduction
 Discovery
 Chemical structure
 Properties of chlorophyll
 Biosynthesis of Phytol chain
 Biosynthesis of Chlorophyllide

3.  Chlorophyll is a green photosynthetic pigment found in
plants, algae, and cyanobacteria.
 Chlorophyll absorbs mostly in the blue and to a lesser extent
red portions of the electromagnetic spectrum, hence its
intense green color.
 Green substance in producers that traps light energy from the
sun, which is then used to combine carbon dioxide and water
into sugars in the process of photosynthesis Chlorophyll is
vital for photosynthesis, which helps plants get energy from
light.
 Chlorophyll molecules are specifically arranged in and around
pigment protein complexes called photosystems, which are
embedded in the thylakoid membranes of chloroplasts.
Plants are perceived as green because
chlorophyll absorbs mainly the blue
and red wavelength and reflects the
green.

4.  Chlorophyll was first isolated and named by Joseph
Bienaime Caventou and Pierre Joseph Pelletier in
1817.
 After initial work done by German chemist Richard
Willstatter spanning from 1905 to 1915, the
general structure of chlorophyll a was elucidated
by Hans Fischer in 1940.
Joseph Bienaime Caventou Pierre Joseph Pelletier
Richard Willstatter

5.  Chlorophylls are numerous in types, but all are defined by
the presence of a fifth ring beyond the four pyrrole-like
rings.
 Most chlorophylls are classified as chlorins, which are
reduced relatives of porphyrins (found in hemoglobin).
 They share a common biosynthetic pathway with
porphyrins, including the precursor uroporphyrinogen III.
 Unlike hemes, which have iron at the center of the
tetrapyrrole ring, chlorophylls have magnesium at the
center.
 The chlorin ring can have various side chains, usually
including a long phytol chain.

6.  The most widely distributed form in terrestrial plants is chlorophyll a.
 The chlorophyll molecule is made up of two moieties of distinct origin—chlorophyllide
and phytol.
 The phytyl side-chain derives from the plastidic isoprenoid biosynthetic pathway.
 The initial steps in chlorophyllide synthesis, from the biosynthesis of δ-aminolevulinate
to protoporphyrinogen IX, occur in the soluble phase of plastids, whereas the
subsequent steps are membrane-bound.
 The initial steps leading to the synthesis of uroporphyrinogen III are common to all
tetrapyrroles that are synthesized in chloroplasts (chlorophyll, heme,
phytochromobilin, siroheme).

7.  Chlorophyll is found in virtually all photosynthetic organisms including green plants,
cyanobacteria and algae.
 It absorbs energy from light and this energy is then used to convert carbon dioxide to
carbohydrates.
 Chlorophyll have a tadpole like structure. There is porphyrin head and a phytol tail.
 Porphyrin head consists of four pyrrole rings with a central magnesium atom
connected with four nitrogen atoms.
 The long hydrophobic phytol tail is lipid soluble and it is anchored in the thylakoid
membrane.

8.  The head is hydrophilic and generally lies in the surface of the membrane.
 The intense green color of chlorophyll is due to its strong absorbencies in red and blue
regions of the spectrum. Because of these absorbencies the light it reflects and
transmits appears green.
 Due to the green color of chlorophyll , it has many uses as dyes and pigments.
 It is used in coloring soaps, waxes, oils and confectioneries.
 Chlorophyll a and chlorophyll b :soluble in a alcohol, ether, benzene, acetone, and
insoluble in water.
 The melting point of chlorophyll a is 152°C and the of chlorophyll b is 125°C.

9.  It has antibacterial properties.
 It removes harmful toxins from the body.
 It speeds up would healing.
 It stimulates bowel function.
 It helps in reducing weight.
 It strengthens the immune system.
 It lowers blood pressure.
 It protects against carcinogens.
 It lowers cholesterol.
 It purifies blood.

10.  The 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway provides
isopentenylpyrophosphate (IPP) for synthesis of the central intermediate geranylgeranyl
diphosphate (GGDP) for plastidial isoprenoids.
 This process involves the following steps:
i) The first step of the MEP pathway combines glyceraldehyde3-phosphate and
pyruvate—a reaction catalyzed by 1-deoxyD-xylulose 5-phosphate synthase to form
deoxy-D-xylulose 5-phosphate.
ii) The second step involves a reductive isomerization by a 1-deoxy-D-xylulose 5-
phosphate reductoisomerase on deoxy- D-xylulose 5-phosphate and yields MEP (2C-
methyl-D-erythritol 4-phosphate).

11. iii) The introduction of a cytidyl moiety by 2-C-methyl-D-erythritol 4-phosphate
cytidylyltransferase to produce 4-diphosphocytidyl-2C-methyl-D-erythritol.
iii) 4-diphosphocytidyl-2C-methyl-D-erythritol is phosphorylated by 4-(cytidine
5’diphospho) 2-C-methyl-D-erythritol kinase and then cyclized after loss of the cytidyl
group to yield 2-C-methyl-D-erythritol 2,4cyclodiphosphate _reaction catalyzed by 2-C-
methyl-D-erythritol 2,4-cyclodiphosphate synthase.
iv) The active C5 unit (IPP) and DMAPP are then formed in final steps catalyzed by two
enzymes: 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase and reductase.

12.  IPP( isoprenoid pyrophosphate) once synthesized undergoes a sequential
series of condensation reactions to form geranylgeranyl diphosphate (GGDP).
 GGDP is a central intermediate in the synthesis of plastidic isoprenoids:
chlorophylls (phytyl side-chain), carotenoids and prenylquinones (isoprenoid
side-chains.

13. Glyceraldehyde 3-phosphate + pyruvate
1-deoxy-D-xylulose 5-phosphate
2C-methyl-D-erythritol 4-phosphate
4-diphosphocytidyl-2C-methyl-D-erythritol
4-diphosphocytidyl-2C-methyl-D-erythritol-2-phosphate
2C-methyl-D-erythritol 2,4-cyclo-diphosphate
1-hydroxy-2-methyl-2-butneyl 4-diphosphate
isopentenyl pyrophosphate dimethylally diphosphate
GGPP
CHLOROPHYLL
(phytol)

14. Synthesis of Protoporphyrin IX :
 The first step involves the conversion of L-glutamate to glutamate 1-semialdehyde
which is catalysed by the enzyme Glutamyl-tRNA synthetase .
 Glutamate 1-semialdehyde gets converted into 5 aminolevulinic acid by the enzyme
Glutamate 1-semialdehyde aminotransferase 1.
 Enzyme aminolevulinate dehydratase then converts 5 aminolevulinic acid into
Porphobilinogen.
 Porphobilinogen gets converted into Hydroxymethylbilane by the enzyme
Porphobilinogen deaminase.

15.  Hydroxymethylbilane in the presence of enzyme Uroporphobilinogen III synthase
forms Uroporphobilinogen III.
 Uroporphobilinogen III then in the presence of enzyme coproporphyrinogen III
decarboxylase and oxidase forms Coproporphyrinogen III.
 Corproporphyrinogen III in the presence of enzyme protoporphyrinogen oxidase
forms Protoporphyrin IX.
 The first enzymes of the pathway (i.e. up to protoporphyrinogen IX oxidase) are
located in the stroma.

16.  The second phase of chlorophyll biosynthesis is associated with chloroplast membranes in
a complex manner.
 This involves the formation of Mg-protoporphyrin IX, catalyzed by the enzyme Mg -
chelatase.
 Mg-chelatase catalyses the reaction by inserting Mg2+ protoporphyrin IX.

17.  This involves the formation of Mg-protoporphyrin IX Monomethyl Ester from Mg-
protoporphyrin IX and the reaction is catalysed by Mg-protoporphyrin IX
methyltransferase.
 Mg-protoporphyrin IX Monomethyl Ester then gets converted into Protochlorophyllide
in the presence of enzyme Mg-protoporphyrin IX Mecyclase.
 protochlorophyllide in the presence of enzyme protochlorophyllide oxidoreductase
forms Chlorophyllide a.

18.  The chlorophyll synthase performs the esterification of chlorophyllide (a and b),the
last step of chlorophyll biosynthesis.
 The cholorophyllide a on addition with phtyl-PP in the presence of enzyme
chlorophyll synthase yeilds chlorophyll a.
 Chlorophyll b is then formed from chlorophyll a by the enzyme chlorophyll a
oxygenase.

20. https://www.sciencedaily.com
Chloroplast Proteomics and the Compartmentation of
Plastidial Isoprenoid Biosynthetic Pathways ( Molecular
plant) _ Joyard et al 2009
https://www.worldofmolecules.com