2. ๏ Primary metabolism: known function
๏ Example of primary metabolites:
๏ผ Pyruvate
๏ผ Ethanol
๏ผ Lactic acid
๏ Primary metabolism is used for:
๏ผ Growth and development of hyphal structure
๏ผ Energy metabolism
๏ผ Regulation of metabolism
๏ผ Intermediate in biosynthesis of compound
๏ Widely distributed in nature
3. ๏ Often lack known function
๏ Found in few species or genera
๏ Specialised distribution peculiar to individual species or
small groups of species: idiosynchratic- very
unique, special and specific
๏ Production of these compounds often after growth has
stopped. Why?
- limitation/nutrients depression
- Contamination- competition
- Fungal cell death due to physical and chemical factors
4. Primary metabolism Secondary metabolism
Function are known Function are usually unknown- lack
Widely distributed in nature Only found in few species or genera -
idiosynchratic
Usually used for growth, energy and as
intermediate
Produced usually after growth has
stopped
Examples: Pyruvate, lactic acid, ethanol Examples:
Penicillin, cephalosporin, gibberellin, lo
vastatin
7. ๏ What are the reasons for interest in secondary
metabolites?
๏ industries:
i. Antibiotic: Penicillin and cephalosporin
ii. Itaconic acid: textile industries
iii. Gibberellin: plant growth regulator
iv. Animal feed
๏ Pigment
๏ Bioluminiscences
8. ๏ Mycotoxin
๏ผ Aflatoxin: attack crops and cereals, by Fusarium.
๏ผ Zearalenone: attack animals (poultry and swine)- cause
infertility and abortion. Can be absorbed by human
skin.
๏ Phytotoxin and plant growth regulators produced by
pathogenic fungi
๏ผ HC toxin: attack Zeamays (maize), from Cochliobolus
carbonum, it is a host specific toxin
๏ผ Amatoxin: by Amanita phalloides- A subgroup toxin
๏ผ Gibberellin and cytokinins: plant growth regulators
9. ๏ Classified based on 5 main metabolic sources:
1. Amino acid
2. Shikimic acid pathway for biosynthesis of aromatic
amino acid
3. Polyketide biosynthetic pathway from Acetyl CoA
4. Mevalonic pathway from Acetyl CoA
5. Polysaccharides and peptidopolysaccharides
*3 and 4- most involved in production of secondary
metabolites
*amino acid- biosynthetic origins in gycolysis and TCA cycle
10. ๏ Many Ascomycetes and several bacteria
(e.g., Streptomyces) make the ฮฒ-lactam
antibiotic, Penicillin and Cephalosporin.
๏ Penicillium chrysogenum, Aspergillus
nidulans, Acremonium chrysogenum
๏ The precursor substrates for biosynthesis ฮฒ-lactam are
amino acids
- Show the clear interaction of secondary
with primary metabolites.
11. ๏ Penicillins and cephalopsorins share the initial steps of
their biosynthesis, beginning with Val, Cys and ฮฑ-
aminoadipic acid.
๏ These amino acids have their origins in the TCA
๏ Naturally occurring penicillins produced in the absences of
the side chain precursor supplement in the medium all
contain fatty acid side chains
๏ Peniciilin F, Penicillin K โderivatives of penicillin with
different side chains
12. ๏ The evolutionary origin of secondary metabolic
pathway comes from sequence comparisons of the
cloned genes
๏ The genes cloned from Penicillin
chrysogenum, Aspergillus nidulans, Acremonium
chrysogenum
๏ Revealed in comparison with the analogous genes from
the prokaryotes Streptomyces lipmanii and S.
clavuligerus, striking similarity in both the nucleic
acid and amino acid sequences.
13. ๏ Common evolutionary origin and cross kingdom
transfer of the genes may have occurred about 370 mil
years ago
๏ P. chrysogenum produces 17 secondary metabolites
๏ PATULIN- polyketide-related antibiotic produced by
P. Urticae also known as P. Patulum and P.
griseofulvum
๏ Biosynthesised by acetate malonate pathway
14. ๏ Aspergillus flavus and A. parasiticus
๏ Carcinogenic properties
๏ Belong to the polyketide family of secondary
metabolites derived from Acetyl CoA
Aspergillus flavus- stained by
lactophenol blue