Understanding Phenolic Compound Biosynthesis via the Shikimate Pathway

[Music] [Music] welcome to nptl online certification

course on pharmacognosy and metabolic engineering we'll now go to lecture number

48 where I will speak about the origin of phenolic

via simate pathway so phenolic compounds are very important because they plays important role very important role so I

will uh talk about that but let me briefly tell what are the concepts to be covered in this lecture uh so as you see

here that the we'll first cover the siket coreset pathway and then we'll talk about the regulation

of simate pathway and then we'll talk about the biosynthesis of aromatic amino acids okay so phenolic as we say so

phenolic is basically a phenol counting hydroxy group we come to that so why we study phenolic and phine propanoids so

phenolic is a big name so it starts with mostly it starts with Phile propanoids so Phile propanoids are generally C6 C3

compounds so right for example this is C6 and this is

C3 so this is a three carbon and this is a six carbon so these are Phile

propanoids so why we study Phile propanoids because phal propanoids consist of diverse

subgroups uh like kumarin like ligant like ligins like subin steelb flavonoids tannins so most of this we are going to

cover in the uh subsequent class in the lecture number 49 okay let's see so this is phenol

phenol is just a simple Benzene ring with a hydroxy group so any compound

containing a benzin ring with a hydroxy group will come under phenolic but again there are compounds

where hydroxy group is not there but still we put it under phenolic uh classic example is this is a camic

acid so here there is no hydroxy group but still we'll call it phenolic compound

because this is the origin of uh phenolic Moes so here from where it starts from phine alanin it converted

into camic acid so you can say this is the basic precursor of the phenolic compounds and apart from that there are

a lot of phy alenin uh derivative phenolic compounds are there uh which contributes to the Rose fragrance like

Phile ethanol then Phile ethy acetate so where also there is at four position no hydroxy is there but still we'll call

under phenolic compounds so what we are going to see that how phenolic compounds originate so it basically originates

from primary metabolism as you see here erros Force phosphate and finol pyet these two joins

and eventually they create the simate pathway uh which where simate is one of the major intermediates and then it

produces chorismate so sometimes we call it Sate Kismet pathway from Kismet pathway uh there are two different

routes one root contributes to the in case of indol alkaloids so where tryptophan converted into tryptamine by

tryptophan decarbox and we have also said how tryptophan originates via indol and the

other roote which is of much concern in these classes is basically the formation of tyrosin and phy alanin so tyrosin and

phy alanin these are the tropen these three are aromatic amino acids and uh the difference between tyrosin and phy

alanin is this that in case of phy alanin this is the structure of finy

aronin and when this fourth position o is added then it becomes tyrosin so let us now see in the in

details about the uh about the simate coris pathway the first step is basically arios Force phosphate joining

with phenol pyate here and the E1 what I have mentioned here is basically the first enzyme which is called DP synthes

d a HP synthes also nowadays it is called DHS as well uh yeah

DHS it is also called DHS as another abbreviations so this is three deoxy D Arab know so let me write it for you

three deoxy D

ARA bino Hep

loic acid 7 phosphate which is called d a HP

okay so this is dhp this dhp in the next step it is converted

into three dehydroquinate so the three dehydroquinate the enzyme which is

E2 E2 is basically dehydro queet synthes

dehydroquinate synthes we also call dhqs next enzyme is E3 E3 basically dehydroquinate converted

into dehydro simate dehydroquinate converted into dehydrate so or dehydr cimic acid so the

enzyme is dehydroquinate dhq stands for dehydroquinate and then

simate uh simate dehydrates dehydrates means basically a molecule of water will go out so you can

show it here H2O so this forms dehydrate so the next one is the

E4 E4 is also this is dehydroquinate uh dehydroquinate simate

dehydrogenase de hydrogenous so that is called dhq

dash s DH dehydr sec dehydrogen okay here the abbreviations is also same for the other

one uh so here also is uh DH DH q s DH abbreviation is same for both the

cases whereas the first one is a dehydratase and second one is a dehydrogenase so when is a dehydrogen

then it requires iph and

liberates np+ okay so it forms simic acid which which I mentioned that this is one of

the intermediate major intermediate that is why the pathway is named as simic acid

next what happens simate will be converted into simate 3 phosphate so there will be the addition of phosphate

that means ATP is required so you can add an ATP it liberates ADP which forms simate

3 phosphate and this Sim 3 phosphate uh then what is the

enzyme enzyme is basically it is as phosphate this is called simate kyes

simate KES SK

okay and the next one uh simate three phosphate with addition of phosph pyate it form

epsp so epsp is again another major product of this pathway epsp and the enzyme E6 is

called epsp synthes so and then E7 which

converts epsp 2 coris smat so the E7 is basically it's it's CS we can say

it is cisat synthes uh c h o r i s m a tmate

synthes or CS and uh this one is

PPS okay here one important thing I'd like to tell here that uh one of the very well-known herbicide is glyphosate

so glyphosate is applied uh to get rid of the weeds so basically it stops the simate pathway

and that thus blocks the formation of aromatic amino acid eventually the metabolism and the plant dies

particularly the diots and what what it happens that glyphosate basically blocks here so it's

basically a competitive inhibitor of this enzyme which is epsp synthes and therefore the pathway blocks

so if one study the pathway leading to formation of the different phenolic compounds uh if a metabolism can be

studied in cell and orgal culture there glyphosate addition can make impact on the end product uh so regulation is so

stringent so this is in brief about the uh pathway leading to the formation of Kismet from arthos for forest and

dihydroxy acetone phosphate next slide what we will see that

coris uh what we see that will be converted into uh this is called prenate so the prenate is

basically called corate mutas so this enzyme so I will call c m CM stands for Kismet

mutas then comes uh this pranet so pranet is here prenate will be converted into El arogenate by another enzyme

which is called prefet aminot transference uh cmic acid prenate to prenate will

convert yeah it's called prefet aminot transference we will also call this in brief as

P the enzyme is called P E9 what the new name is p so p means that prenate aminot transfer is

so it's written here preate aminot transfer is okay and next what happens one aerogenic acid is formed so but this

requires but this requires uh glutamate and which Liber

two Oxo glutarate okay

and then it converted into arogenate so arogenate from there there are two pathway exist one is arogenate

dehydrates uh so ADT so I can give a name ADT here this

one is ADT ADT stands for arogenate dehydrogen dehydrate is so

arog genate dehydrates when we say so then we have

to show that a water molecule is released as well as a molecule of carbon dioxide is also released so which

converts arogenate to tyrosin the other one is that arogenate dehydrogenase which

is ADH ADH which is arogenate dehydro genus when uh it

requires again it here also a molecule of carbon dioxide

liberates and it requires this energ pH so because of shortage of space I'm not showing that

and it finally that is why ultimately it makes uh phy alanin or tyosin if arogenate dehydrogen is work

it makes phy alanin if arogenate dehydrate is work it makes thyrosin and in Plants both the pathway is operating

but there is a fine balance between two and we will see much later that the volatile benzenoids benzenoids originate

from this Phile propanoids so those uh and they they emit from different flowers ponia was used as a model so

scientists what they did they tried to control the path at this level ADH and ADT and that basically makes impact on

the final product so that means the control is far ahead than the it's not in the penultimate step but in the very

long distal Step Ahead now uh what I say that sub cellular

localization so the pathway mostly operate in the plastid so so uh that means the cormic acid

onwards the pathway is operating in the plastid so like coris mutas okay and then this prenate aminot

transfer is then arogenate uh dehydrogen the arogenate dehydr both are uh operating inside the plastid and

thyrosin and pyerin are produced inside the plastid okay and from there maybe they are uh emitting out into the cytool

for different function whereas cytosolic Phile pyate Pathways also exists okay where phy alenin is produced from

chorismic Acid so here you see chorismate mutas one this is cm1 which is operated in the plased

whereas cm2 coris mutus 2 which convert cormic to penic acid this is isopor but this

basically localized in the cytool which makes pranic acid then then there may be a Preen

dehydrates which is still not clear but which makes Phile pyate this Phile pyate bile Pate again

aminot transference which basically makes the Phile alanin so uh so this is the uh

cytosolic root of formation of pheny ananin uh from the simate pathway okay so now both phy alanine and

tyosin are formed so this is in a nut cell the pathway now what I am showing here is basically this is from

a uh review article which is published in current opinion in plan biology 2022 so where basically it focused on

that the the simate corate pathway the main regulation occurs at the very first stage which is this DP synthes uh which

I have also said that it is nowadays called DH DHS also there are different different isoforms exist like dhs1 dhs2

DHS 3 and that basically plays important role in controlling the pathway so basically uh some feedback regulation

work so when uh sufficient amount of thyrosin is produced then a signal goes and stops

the dhs2 the red one so which isopor is basically controlling

the tyos whereas the uh even coris can also be controlled by that even much later the

cafet which plays important role in lignification and other cic acid EST that is also being controlled at the

very early stage in the pathway uh so okay uh so uh so DHS is important that is why I made it

otherwise the whole pathway modeless I have covered so only two tell you that the uh where the regulation lies and

also another important point this from tyos different metabolites originate like

tocoferol vitamin E plastoquinones isoquinoline Alco we have covered that cogenic glycosides we have not covered

in that details betal lens whereas from phy alanin the most important products are ligin stannin

subin flavonoids anthoine kumarin steel bin salicylate this we are going to cover soon and tryptophan is also being

controlled by the dhs2 and we have we have seen that tropen contributes to indol

pathway now uh multiple regulations of plant DHS activity as indicated by the pink box so so this uh these DHS genes

are basically nuclear encoded genes and then the once the DHS protein is produced it mostly moved into the

plastid okay so basically this is showing the movement into the plastid and there it basically performs it

function and there m manganese ion plays an important role and it performs different functions so basically uh it

it it plays important role in this feedback regulation this is what I mean to say

and there is also cobal dependent cytosolic DHS activity has also been discovered in recent

years so but uh this is not fully known and this is again from the latest

information available in current opan in plant biology so the take-home message is that DHS or dhp synthes is very

important enzyme that is the regulatory enzyme which is controlling the s cmate pathway ultimately the Phile

propanoid pathway and uh that is mostly it moved into the into the plastid but that is also the evidence of cytosolic

DHS so uh so this is we have discussed the simate pathway so simate pathway forms

the uh Phile alanin here we have discussed so Phile Aline are C6 C3 compounds C6 C3 compounds and from there

different other C6 C3 compounds originate like camic acid karic acid Kumar Co and then what happens from this

C6 C3 then again this is C6 C3 and from there it forms lignin which is basically C6 C3 and digin is multiple n so it's a

polymer and it can also form simple phenolics like uh c6c C6 C1 benzoic acid C6 C2 compounds even even the

C6 C3 C6 which is called flavonoid compounds this can also produced and this when joins in multiple unit it

forms the condensed tanins of proanthocyanins also from sikic Acid the G IC acid is

produced and which plays important role in forming the large polymer hydrolyzable tannins which I will show

in the next class so the point here is this that simate arogenate pathway ultimately contributes to phy

alanin or hydroxy camic pathway so phy alanin to camic acid so the camic acid is hydroxy camic acid when this four o

when this camic acid when it's converted into four hydroxy Amic acid which is called parakum aric acid we'll see that

so that is why it is called hydroxycinnamic acids so that is an important molecule from where uh from

from that molecule different compounds originate so if you remember at the origin of uh when you talk about the

origin of specialized metabolites so from the precursor uh it produces

the the main P product and from P under goes different transformation so basically these are nothing but

different transformation which occurred in different plants sometimes it occurred in uh several of these

reactions occur in different plants for example um 1 to 5 so what is showing here 1 to 5 1 2 3 4 5 so 1 2

5 uh so this basically leads to formation of flavonoids so this is flavonoids and

then number two is basically steel Bane we'll talk all this in the subsequent class okay then style of Pyon we leave

it bop phenon bop phenon actually leads to the formation of uh this um zenthon is number four is very important

ultimately it forms the zenthon and this actually contributes to antoin and then what important is this

dihydro Camile 7 to hydroxy Camile alcohol so this is basically the component of ligin monomer which is

called monol liol then number eight is basically hydroxy benzoid these are small

molecules uh so which includes vanilline also and then number nine is basically hydroxy kumarin so kumarin you will find

in several plants including ellify spes and then conjugations uh which leads to hydroxy

Esters number 10 we will see that in due course and amides so basically this is the central

role of hydroxy cinam towards the formation of different uh Phile proponent compounds

so these are the trans transformation P P1 P2 P3 P4 P5 so p is basically the hydroxycinnamic acid so now the major

class of phenolics I will end this class briefly telling this but again I will bring this issue in the subsequent class

so C6 are called Simple phenols examples are caol C6 C1 are the hydroxy benzoid C6 C2 are aceto phenon

C6 C3 which are Phile propin hydroxyamines kumarin then C6 C4 are nap quinon we will talk

about one such Napo quinon pigments towards the end of this phenolic classes uh cin then C6 C1 C6 is basically the

zenthon whereas C6 C2 C6 which is still bin and

the C6 C3 C6 are basically flavonoids and then C6 C3 constitute the ligin uh with n okay and then so on then

C6 c3n which is condensed tenin it's basically the polymer uh so we will talk

about this important uh groups in the subsequent classes like we'll talk about liance which is

basically two molecules of monol lion Li monomer joints and form liance we we'll mention about that

and so many interesting things so this is basically the major classes of phenolic all these originate from this

simate Kismet pathway and these are some of the structures uh with this uh so like

uh hydroquinon like kol for hydroxy benzo acetophenone cafeic acid

eugenol we'll talk about that uh and and then R veratrol will talk about that Tetra hydroxy janon we talk about that

quatin will beefly talk pinoresinol will talk and so many so on so with this I end this class thank you very much