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Published on January 13, 2012

Author: nishikaa


SECONDARY METABOLISM IN FUNGI: SECONDARY METABOLISM IN FUNGI PRESENTATION BY: NISHIKA BHAN METABOLISM: METABOLISM set of chemical reactions that happen in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Primary Metabolism: Primary Metabolism Encompasses reactions involving those compounds which are formed as a part of normal anabolic and catabolic processes. These processes take place in most of the cells of the organisms. A primary metabolite is directly involved in normal growth, development, and reproduction. Eg. Alcohol. Secondary Metabolism: Secondary Metabolism is a term for pathways and small molecule products of metabolism that are not absolutely required for the survival of the organism. Metabolites are the intermediates and products of metabolism. A secondary metabolite is not directly involved in those processes, but has an important ecological function. Examples include antibiotics and pigments. Categories: Categories Mycotoxins : Alfatoxins, Ochratoxins, Citrinin Antibiotics : Penicillin, Griseofulvin, Cyclosporin Alkaloids : Ergot Amino acids : alpha- amanitin Mycotoxins: Mycotoxins Refers to the toxic chemical products produced by fungi. The reason for the production of mycotoxins is not yet known; they are neither necessary for growth nor the development of the fungi. PowerPoint Presentation: Mycotoxicoses is the term used for poisoning associated with exposures to mycotoxins. Symptoms of a mycotoxicosis depend on the type of mycotoxin; the concentration; as well as age, health, and sex of the exposed individual. Mycotoxins have the potential for both acute and chronic health effects via ingestion, skin contact, and inhalation. These toxins can enter the blood stream and lymphatic system, they inhibit protein synthesis, damage macrophage systems and inhibit particle clearance of the lung. Aflatoxins : Aflatoxins naturally occurring mycotoxins that are produced by many species of Aspergillus , most notably Aspergillus flavus and Aspergillus parasiticus . are among the most carcinogenic substances known. PowerPoint Presentation: native habitat of Aspergillus is in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration. invades all types of organic substrates whenever conditions are favorable for its growth. Favorable conditions include high moisture content (at least 7%) and high temperature. The toxin can also be found in the milk of animals which are fed contaminated feed. Pathology : Pathology No animal species is immune to the acute toxic effects of aflatoxins including humans; however, humans have high tolerance for aflatoxin exposure. High-level aflatoxin exposure produces an acute hepatic necrosis, resulting later in carcinoma of the liver. Children are particularly affected by aflatoxin exposure which leads to stunted growth and delayed development. Chronic exposure also leads to a high risk of developing liver cancer. Medical research indicates that a regular diet including vegetables such as carrots, celery and parsley, reduces the carcinogenic effects of aflatoxin. Citrinin: Citrinin is a mycotoxin originally isolated from Penicillium citrinum . found to be produced by a variety of other fungi which are used in the production of human foods such as grain, cheese, etc. Toxicity : Toxicity Citrinin acts as a nephrotoxin in all species in which it has been tested, but its acute toxicity varies. It induces mitochondrial permeability pore opening and inhibits respiration by interfering with complex I of the respiratory chain. Citrinin producers: Citrinin producers Aspergillus niveus Aspergillus ochraceus Aspergillus oryzae Aspergillus terreus Monascus ruber Monascus purpureus Penicillium citrinum Penicillium camemberti Antibiotics : Antibiotics is a substance or compound that kills bacteria or inhibits their growth. belong to the broader group of antimicrobial compounds, used to treat infections caused by microorganisms, including fungi and protozoa. The term "antibiotic" was coined by Selman Waksman in 1942. Griseofulvin: Griseofulvin also known as Grisovin is an antifungal drug that is administered orally. is used both in animals and in humans, to treat fungal infections of the skin and nails. It is derived from the mold Penicillium griseofulvum . Mechanism : Mechanism It binds to keratin in keratin precursor cells and makes them resistant to fungal infections. Treatment of fungal infections : Treatment of fungal infections Tinea capitis (ringworm of the scalp) Tinea corporis (ringworm of the body) Tinea pedis (athlete's foot) Tinea barbae (barber's itch) Tinea cruris (ringworm of the thigh) Tinea barbae (barber's itch) Common brand names: Common brand names Grifulvin V Gris-PEG S-Fulvin Alkaloids : Alkaloids are a group of naturally occurring chemical compounds which mostly contain nitrogen atoms. Beside carbon, hydrogen and nitrogen, molecules of alkaloids may contain sulfur and rarely chlorine, bromine or phosphorus. Ergotamine: Ergotamine is a secondary metabolite and the principal alkaloid produced by the ergot fungus, Claviceps purpurea , and related fungi in the family Clavicipitaceae . It was first discovered by Arthur Stoll at Sandoz in 1918 and marketed as Gynergen in 1921. possesses structural similarity to several neurotransmitters , and has biological activity as a vasoconstrictor . used medicinally for treatment of acute migraine attacks. Its medicinal usage began in the 16th century to induce childbirth. It has been used to prevent post-partum haemorrhage (bleeding after childbirth). Mechanism of action : Mechanism of action The mechanism of action of ergotamine is complex. The molecule shares structural similarity with neurotransmitters such as serotonin, dopamine, and epinephrine and can thus bind to several receptors. Drug uses : Drug uses Ergotamine produces vasoconstriction. In high doses it can cause thrombosis and gangrene. It can increase uterine contractivity and occasionally is used therapeutically immediately post-partum to decrease uterine bleeding. Ergotamine continues to be prescribed for migraines. Ergot-derived drug to stop postnatal bleeding.: Ergot-derived drug to stop postnatal bleeding. Amino acid: alpha amanitin: Amino acid: alpha amanitin α-amanitin is a cyclic peptide of eight amino acids. is possibly the most deadly of all the toxins found in several species of the Amanita genus of mushrooms, such as A. phalloides , A. virosa and A. bisporigera . is also found in the mushrooms Galerina marginata and Conocybe filaris . Symptoms of poisoning : Symptoms of poisoning α-Amanitin has an unusually strong and specific attraction to the enzyme RNA polymerase II. Upon ingestion, it binds to the enzyme, effectively causing cytolysis of hepatocytes. Around 15% of those poisoned will die within 10 days, progressing through a comatose stage to renal failure, liver failure, hepatic coma, respiratory failure and death. Those who recover are at risk of permanent liver damage. various drugs to counter the amatoxins include intravenous penicillin and cephalosporin derivatives, and, in cases of greater ingestion, can extend to an liver transplant. Scientific use : Scientific use α-Amanitin is an inhibitor of RNA polymerase II. This mechanism makes it a deadly toxin. Mode of inhibitory action : Mode of inhibitory action α-Amanitin (red) bound to RNA polymerase II PowerPoint Presentation: the crystal structure was solved by Dr. Bushnell et al. α-Amanitin interacts with RNA polymerase II . interaction interferes with the translocation of RNA and DNA needed to empty the site for the next round of RNA synthesis. Binding of α-amanitin puts a constraint on enzymes mobility, hence slowing down the translocation of the polymerase and the rate of synthesis of the RNA molecule. References : References Secondary _ metabolism. Mann J,2005, Secondary Metabolism. Secondary_metabolism_regulation. Schardl CL, Panaccione DG, Tudzynski P (2006). "Ergot alkaloids – biology and molecular biology". THANK YOU: THANK YOU

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