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By Assoc.prof.dr.mohd noor abd.wahab
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GluconeogenesisGluconeogenesis
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Synthesis of glucosefrom pyruvate utilizes manyof the same enzymes as Glycolysis.
Occurs incytoplasm (when onlynonsugar C
sourceis supplied.)
*Reversalof Glycolysis process.
Gluconeoenesis
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Three Glycolysis reactions have such a largenegative G∆ that they are essentiallyirreversible.
Hexokinase (or Glucokinase)PhosphofructokinasePyruvate Kinase.
Therefore,these 3 steps ust be bypasse!in Gluconeogenesis. "thers reactions use the
sae en#ye as in Glycolysis.
GluconeogenesisGluconeogenesis
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Gluconeoenesis
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Glucose-6-phosphatase
Fructose-1,6-bisphosphatase
glucose Gluconeogenesis
Pi
H2O
glucose-6-phosphate
Phosphoglucose Isomerase
fructose-6-phosphate
Pi
H2O
fructose-1,6-bisphosphate
Aldolase
glyceraldehyde--phosphate ! dihydro"yaceto#e-phosphate
$riosephosphateIsomerase
%co#ti#ued&
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Hexokinase or Glucokinase (Glycolysis) catalyzes:
glucose + ATP glucose-6-phosphate + ADP
Glucose-6-Phosphatase (Gluconeogenesis)
catalyzes:
glucose-6-phosphate + H! glucose + Pi
H O
OH
H
OHH
OH
CH2OH
H
OH
HH O
OH
H
OHH
OH
CH2OPO32−
H
OH
H
H2O1
6
'
(
2
! Pi
glucose-6-phosphate glucose
Glucose-6-phosphatase
Gluconeoenesis
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Glucose-6-phosphatase
Fructose-1,6-bisphosphatase
glucose Gluconeogenesis
Pi
H2O
glucose-6-phosphate
Phosphoglucose Isomerase
fructose-6-phosphate
Pi
H2O
fructose-1,6-bisphosphate
Aldolase
glyceraldehyde--phosphate ! dihydro"yaceto#e-phosphate
$riosephosphateIsomerase
%co#ti#ued&
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Phospho"ructokinase %Glycolysis& cataly)es*
"ructose-6-P + ATP "ructose-#$6-%isP + ADP
&ructose-#$6-%isphosphatase %Gluco#eoge#esis& cataly)es*
"ructose-#$6-%isP + H! "ructose-6-P + Pi
fructose-6-phosphate fructose-1,6-bisphosphate
Phosphofructo+i#ase→
CH2OPO32−
OH
CH2OH
H
OH H
H HO
O
6
'
(
2
1 CH2OPO32−
OH
CH2OPO32−
H
OH H
H HO
O
6
'
(
2
1
ATP ADP
Pi H2O
← Fructose-1,6-biosphosphatase
Gluconeogenesis
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Glyceraldehyde--phosphateehydroge#ase
Phosphoglycerate i#ase
.#olase
P.P /arbo"y+i#ase
glyceraldehyde--phosphate
0A! ! Pi
0AH ! H!
1,-bisphosphoglycerate
AP
A$P
-phosphoglycerate
Phosphoglycerate utase
2-phosphoglycerate
H2O
phosphoe#olpyruate
/O2 ! GPG$P
o"aloacetate
Pi ! AP
H/O− ! A$P
pyruate
Pyruate /arbo"ylase
Gluconeogenesis
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$ypass of Pyruvate Kinase%
Pyruvate Kinase (last step of Glycolysis) cataly#es%
phosphoenolpyruvate & 'P pyruvate & 'TP
or bypass of the Pyruvate Kinase reaction,
cleavage of * +P bon!s is reuire!.∆ G for cleavage of one +P bon! of 'TP isinsufficient to !rive synthesis ofphosphoenolpyruvate (P-P).
P-P has a higher negative ∆ G of phosphatehy!rolysis than 'TP.
Gluconeoenesis
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'ypass o" Pyruate inase ( enzy*es):
Pyruate ar%oxylase (Gluconeogenesis) catalyzes:
pyruate + H!,- + ATP oxaloacetate + ADP + Pi
PP ar%oxykinase (Gluconeogenesis) catalyzes:
oxaloacetate + GTP PP + GDP + !
C
C
CH2
O O−
OPO32−
C
C
CH3
O O−
O
ATP ADP + Pi C
CH2
C
C
O
O O−
O−
O
HCO3−
GTP GDP
CO2
pyruate o"aloacetate P.P
Pyruate /arbo"ylase P.P /arbo"y+i#ase
Gluconeoenesis
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.hen gluconeogenesis is actie$ oxaloacetate is /ierte/to "or* glucose0 !xaloacetate /epletion hin/ers acetyloA entry into re%s ycle0 The increase in 1acetyl oA2actiates Pyruate ar%oxylase to *ake oxaloacetate0
PyruvateCarboxylase(pyruvate
oxaloactate)is allostericallyactivated byacetyl CoA.
[Oxaloacetate]tends to belimiting forKrebs cycle.
Glucose-6-phosphatase
glucose-6-P glucose
Gluco#eoge#esis Glycolysis
pyruatefatty acids
acetyl /oA +eto#e bodies
o"aloacetate citrate
rebs /ycle
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PEP Carboxykinasecatalyzes ATP-dependentoxaloacetate PEP. It is thought to proceed in 2
steps: Oxaloacetate is firstdecarboxylated to yield a pyruvateenolate anion intermediate.
Phosphate transfer from ATP then yields
phosphoenolpyruvate (PEP).
CC
CH2
O O−
OPO32−
C
CH2
C
C
O
O O−
O−O
CO2
C
C
CH2
O O−
O−
GTP GDP
o"aloacetate P.P
P.P /arbo"y+i#ase 3eactio#
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3n the %acterial4 "ungi enzy*e$ATP is Pi /onor instea/ o" GTP0
3n this crystal structure o" Saccharomyces cerevisiae PPar%oxykinase$ pyruate is atthe actie site as an analog o"PP4 oxaloacetate0
A *etal ion such as 5n+ is reuire/ "or the PP
ar%oxykinase reaction$ in a//ition to a 5g+ ion that
%in/s 7ith the nucleoti/e su%strate at the actie site0
5n+ is thought to pro*ote Pi trans"er %y interacting
si*ultaneously 7ith the enolate oxygen ato* an/ an
oxygen ato* o" the ter*inal phosphate o" GTP or ATP0
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hesource of pyruvate and
oxaloacetate for gluconeogenesis during
fasting or carbohydrate starvation is
mainly glycogen.
Some amino acids are catabolized to
pyruvate, oxaloacetate, or precursors of
these.
Glycerol, derived from hydrolysis of
triacylglycerols in fat cells, is also a
significant input to gluconeogenesis.
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Glyceraldehyde--phosphateehydroge#ase
Phosphoglycerate i#ase
.#olase
P.P /arbo"y+i#ase
glyceraldehyde--phosphate
0A! ! Pi
0AH ! H!
1,-bisphosphoglycerate
AP
A$P
-phosphoglycerate
Phosphoglycerate utase
2-phosphoglycerate
H2O
phosphoe#olpyruate
/O2 ! GPG$P
o"aloacetate
Pi ! AP
H/O− ! A$P
pyruate
Pyruate /arbo"ylase
Gluconeogenesis
ummary of
!luconeogenesisPat"#ay$
!luconeogenesis
en%yme names inred.
!lycolysis
en%yme names inblue.
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Glucose-6-phosphatase
Fructose-1,6-bisphosphatase
glucose Gluconeogenesis
Pi
H2O
glucose-6-phosphate
Phosphoglucose Isomerase
fructose-6-phosphate
Pi H2O
fructose-1,6-bisphosphate
Aldolase
glyceraldehyde--phosphate ! dihydro"yaceto#e-phosphate
$riosephosphateIsomerase
%co#ti#ued&
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Glycolysis 8 Gluconeogenesis are %oth spontaneous0
3" %oth path7ays 7ere si*ultaneously actie in a cell$ it
7oul/ constitute a 9"utile cycle9 that 7oul/ 7aste energy0
Glycolysis:glucose + AD+ + ADP + Pi
pyruate + ADH + ATP
Gluconeogenesis:
pyruate + ADH + ; ATP + GTP
glucose + AD+ + ; ADP + GDP + 6 Pi
0 Gluconeogenesis expen/s ho7 *any =P >
,0 A "utile cycle o" %oth path7ays 7oul/ 7aste ho7 *any
=P per cycle >
&'
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To prevent the waste of a futile cycle,Glycolysis & Gluconeogenesis arereciprocallyregulated.
Local Control includes reciprocal allostericregulation byadenine nucleotides. Phosphofructokinase (Glycolysis) is inhibited by ATP andstimulated by AMP.
Fructose-1,6-bisphosphatase (Gluconeogenesis) is
inhibited by AMP.
fructose-6-phosphate fructose-1,6-bisphosphate
Phosphofructo+i#ase→ CH2OPO3
2−
OH
CH2OH
H
OH H
H HO
O
6
'
(
2
1 CH2OPO32−
OH
CH2OPO32−
H
OH H
H HO
O
6
'
(
2
1
ATP ADP
Pi H2O
← Fructose-1,6-biosphosphatase
Th it ff t fd i l tid
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Theopposite effects of adenine nucleotides on
o Phosphofructokinase (Glycolysis)
o Fructose-1,6-bisphosphatase(Gluconeogenesis)
insures that when cellular ATP is high (AMP wouldthen be low), glucose is not degraded to make ATP.
When ATP is high it is more useful to the cell to storeglucose as glycogen. >>
When ATP is low (AMP would then be high), the celldoes not expend energy in synthesizing glucose.
>>
!luconeogenesis
!lycolysis
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GLOBALGLOBAL
CONTROLCONTROL
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TRANSLOCATION
AND STORAGECOMPOND
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Environment rarely contains favorable
and ideal condition of nutrients for fungalto growth.
Storage of excess nutrients enables
fungi to survive
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STORAGE COMPOND Storage requirements of growth taes place in all
hyphae components
!yphae fragment function as storage
"rotection from mechanism #
thic wall
protective compound
hydrophobic surface
complex structure $starvation%
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STORAGE COMPOND &iffer from those of plants or bacteria but are similar
to those of animals.
The main storage compound are #'
' (ipid
' Glycogen $) * lined polymer of glucose%
' Trehalose $non * reducing disaccharides%
Trehalose, composed of + glucose residue
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L!p!d
' ften seen as globules in fungal cell
' -p to /0 of cytoplasm made up of lipid
' il drop can de seen in most hyphae of old
compartments
' Glycerol is common and important in water
regulation and metabolic activity in fungi
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L!p!d
'Translocation of lipid was bi * directional in the
same hyphae
'(ipid translocated all direction in the 12-$1unctional 2yceluim -nit%
'"art of mechanism for redistributing energy in
the 12-
3 12- 4 integrated hyphae forms an individualistic organisms
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CARBO"#DRATES2ain translocated carbohydrates
' Trehalose' "olyols $ sugar alcohol%
omycetes absence of the characteristic
fungal carbohydrates
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CARBO"#DRATES
T5E!6(SE
' &erived from common sugars taen from the cells
' Eg #'
7 Trehalose 4 + glucose compound
7 2annitol 4 1ructose
' 5eadily interconverted in hyphae
' Trehalose 4 mycelium
' Trehalose 8 arabitol 4 colony margin
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CARBO"#DRATES
T5E!6(SE
' important in resistance against adverse condition 9
cold, heat, dehydration and etc.
' synthesis and degradation highly regulated
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NITROGEN
' stored as protein' abundant at beginning of degradative cycle
' lectin found freely in cytoplasm
' lectin highly conserved nitrogen storage proteins
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TRANSLOCATION O$
STORAGE COMPND
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TRANSLOCATION IN $NGI
There are different mechanisms for nutrient
translocation in fungi #'
7 "assive
7 "assive 8 active uptae
7 6ctive, cytoplasmic
7 6ctive, pressure driven bul flow
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PASSI%E
:ot required extra energy
:utrients taen by hyphae by simple diffusion
as in water phase
;n non' saturated soil filled with air gaps,
hyphae forms bridges and nutrients can spread
via symplastic or apoplastic diffusion
Eg # Glucose taen at hyphae tips and trehalosediffuse down the < = gradient away from hyphae
tips
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PASSI%E & ACTI%E PTA'E
Similar to passive but nutrients taen in excessof local needs
"roduced steep nutrient gradient inside hyphae
5esult faster delivery of nutrients to mycelium
5equires extra energy for the excess uptae
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ACTI%E( C#TOPLASMIC
6ctive movement in cytoplasm either through#
' movements of organelles' peristaltic vacuole system
2echanisms involve compartmentalization of
nutrients followed by peristaltic movements intubular compartment
Storage compound pacaged in vesicles which
moved at hyphae
6ction of cytoseleton significant in movement
of vesicles along hyphae
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ACTI%E( PRESSRE DRI%EN BL'$LO)
;f excess nutrients are taen, it result in a high
osmotic pressure inside hyphae, water will flowthrough cell membrane
This will create high turgor pressure and water
> nutrient will flow inside mycelium with lessresistance
Energy are use for active uptae and overcome
water flow within hyphae
1ormation of fruiting body is the evidence of
bul flow seen as exudation of water droplet at
the surface
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?idirectional transport shown that #'
Organic carbonHOST HYPHAE TIPS
ROOT
M inerals
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BIOSYNTHESI
S OF FUNGI
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)ha* !s b!osyn*h+s!s,
Th+ prod-c*!on ofn++d+d c+-ar
compo-nds( -s-ay
from s!mp+rmo+c-+s
In fungi, the most important
compound to synthesis :
CHITIN
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C"ITIN
long-chain polymer of a N-acetylglucosamine, aderivative of glucose, and is found in many placesthroughout the natural world. It is the main
component of the cell walls of fungi.
modified polysaccharide which containsnitrogen; it is synthesized from units of N-
acetylglucosamine (more precisely, 2-(acetylamino)-2-deoxy-D-glucose).
Linked by β (1-4) bonds.
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The basic unit is derived from fructose-6-phosphate bythe addition of an amine and an acetyl group from the
amino acid glutamine and acetyl CoA, respectively.
The chitin adds rigidity and structural support to thethin cells of the fungus, and gives protection as well.
described as cellulose with one hydroxyl group on eachmonomer substituted with an acetyl amine group.
This allows for increased hydrogen bonding betweenadjacent polymers, giving the chitin-polymer matrix
increased strength.
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C"ITOSANChitosan is a modified carbohydrate polymer/derived from the chitin component.
Chitosan is a linear polysaccharide composed ofrandomly distributed β!"#$lin%ed D&lucosamine
!deacetylated unit$ and 'acetylD&lucosamine
!acetylated unit$(
Poorly or non acetylated form of chitin(
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Chitosan is obtained by removing enoughacetyl groups (CH3-CO) for the moleculeto be soluble in most diluted acids.
This process) called deacetylation(
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SYNTHESIS OF CHITIN
*irst combined ith a donor molecule) to pro,ide theener&y re-uired for synthesis(
.TP + 'acetyl&lucosamine .DP'
acetyl&lucosamine + Pi
/econd) .DP'acetyl&lucosamine combine ith poly'acetyl&lucosamine to form .DP + chitin(
!Donor +su&ar unit$ + acceptor donor +!acceptor+ su&ar unit$
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C"ITIN S#NT"ASE
Exist inzymogen form then converted into functionalenzyme by partial proteolysis with protease enzyme.
In this state, functional enzyme is formed and readily
to work.
Occur in particles, termed ‘chitosomes’.
Small spheroidal bodies, 40-70 nm diameter,surrounded by a shell. (about 7nm thick).
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CONT…
If presence of an activator (proteolytic enzyme) andsubstrateN-acetylglucosamine, chitosome now canformed chitin microfibril by breaking the shell.
As ‘microvesicles’ in hyphal tips. Extracted from members of all the main chitin-containing fungal groups:(i) Allomyces(ii) Mucor(iii)Saccharomyces
(iv)Neurospora(v)Agaricus.
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SECONDARY
METABOLISM IN FUNGI
Rf t id f tbli
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Refers to a wide range of metabolicreactions whose products are not directlyor obviously involved in normal growth.
Features:
Tend to produced at the end of theexponential growth phase in batch culture or
when growth is substrate-limited incontinuous culture
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Produced from common
metabolic intermediates but by
special en0ymatic pathays
encoded by specific &enes
'ot essential for &roth or
normal metabolism
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Important for commercial or environmental
significancePenicillins (from Penicillium chrysogenum)
Griseofulvin (from P.griseofulvum)-antibiotics produced
commercially from fungi
Carotenoid pigments in conidia fungi such as
Neurospora crassa
Gibberellins-plant hormone for horticulture
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Many secondary metabolites have no obvious roles in
the life of the producer organism, and mutated strains
that do not produce this compound often grow as wellas the wild-type strains in culture.
Instead of that,secondary metabolism acts as an
overspill or escape valve,to remove intermediates from
the basic metabolic pathways when growth is
temporarily restricted.
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Th+ Pa*hway andPr+c-rsors of
S+condaryM+*abo!sm
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A few key intermediates of the basic metabolic
pathways provide starting points for the pathways
of secondary metabolism.
The single most important secondary metabolic
pathway is the polyketide pathway.
The precursor is acetyl-Coa which is carboxylatedto form malonyl-Coa,then three or more molecules
of malonyl-Coa condense with acetyl-Coa to form
chains.
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This chains under&o
cycli0ation)then the rin& systems aremodified to &i,e a ide ran&e of
products such as anti biotic
&riseoful,in!treat dermatophyteinfections$
Another important secondary
metabolic pathay of fun&i is the
isoprenoid pathay for the synthesis
of sterols(
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AcetylCoa is the precursor)but three
molecules of this condense to form
me,alonic acid!1C$ hich iscon,erted to a C isoprene unit(
The isoprene units condense head
totail to form chains under&ocycli0ation and further modifications(
The product in this pathay include
mycotoins of *usarium spp(that &roon moist &rain such as T2 toin and
the trichothecenes(
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EXAMPLE OF SECONDARY
METABOLITES
Penicilins
Mycotoxins
Ergot Alkaloids
Aflatoxins
Sporidesmin
Patulin
Roquefort Cheese
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PENICILLINS
Was discovered by Alexander Fleming in 1929 as a metaboliteof Penicillium chrysogenum .
Most active against Gram-positive bacteria. It prevent thecross- linking of peptides during the synthesis ofpeptidoglycan layer in bacteria cell wall making it weak andsusceptible to osmotic lysis.
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MYCOTOXINS
Diverse range of compounds from differentprecursors and pathway.
Cause toxicity when humans ingest them over arelatively long period of time, from lowconcentrations in improperly stored food.
The problem to detect this toxins is it may takeyears before the effect of exposure become evident.
So to avoid this problem we must storage our food inits proper place.
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OTHER TOXINSToxin Representative
fungi
Foodstuff Effects
Aflatoxins Aspergillus flavusand
A. parasiticus
Peanuts,
oilseeds
Nephrotoxic,
Hepatocarninomas
Ergot alkaloids Claviceps purpurea Cereals,
grasses
Nuerotoxic
Fuminosins Fusarium moniliforme Maize Human esophagealcancer
Ochratoxin A Some Aspergillusand
Penicillium spp.
Grain crops Nephrotoxic and kidney
carcinoma
Patulin Penicillium expansum
and Aspergillus
clavatus
Apples Contact edema and
hemorrhage
Sporidesmin Pithomyces chartarum Grass Facial eczema of sheep
and cattle
Sterigmatocysti
n
Aspergillus spp. Grain, Oilseeds Hepatocarcinogen
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STRUCTURE OF SOME TOXINS
Ergotalkaloids
Aflatoxins
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Sporidesmin
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ROQUEFORT CHEESE
Roquefort cheese and other blue-veined cheeses areproduced from goat milk that are inoculated with
the fungus Penicillium roqueforti.
The cheese contain low levels of the mycotoxinroquefortinebut these levels are not considered tobe hazardous.
The end