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Biologically important heterocycles

Biologically important heterocycles. Alice Skoumalová. Heme complexed with protein in hemoglobin 4 pyrrole rings coordinated with Fe 2+ side chains: methyl, propionyl, vinyl carries oxygen to the tissues. Bilirubin degradation product of heme (cleavage and reduction)

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Biologically important heterocycles

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  1. Biologically important heterocycles Alice Skoumalová

  2. Heme • complexed with protein in hemoglobin • 4 pyrrole rings coordinated with Fe2+ • side chains: methyl, propionyl, vinyl • carries oxygen to the tissues • Bilirubin • degradation product of heme (cleavage and reduction) • excreted in the bile • jaundice

  3. Tryptophan • an amino acid (serotonin and melatonin precursor) • Serotonin • a neurotransmitter (mood control) • many antidepressant drugs increase the level of serotonin in the brain • Melatonin • a hormone (produced in response to the light-dark cycle → regulates circadian rhythms) • an antioxidant → protective effects

  4. Histidine • an amino acid (histamine precursor) • Histamine • a neurotransmitter (the major mediator of the allergic response → vasodilation, bronchoconstriction) • antihistamines (block histamine from binding to its receptor) • Biotin (vit. H) • in liver, egg yolk, yeast products, legumes, nuts • function: carboxylation (the coenzyme of the carboxylases)

  5. Thiamine (vit. B1) • contains two heterocyclic rings • in grain, yeast products, pork • its deficiency (beriberi → neurological disturbances, cardiac insufficiency, and muscular atrophy) • function: oxidative decarboxylation • Tocopherol (vit. E) • in cereals, liver, eggs, seed oil • function: antioxidant in membranes

  6. Nicotinamide (niacin) • in meat, yeast products, fruit, vegetables • its deficiency (pellagra → skin damage, digestive disturbances, depression) • function: in the coenzymes NADH and NADPH (dehydrogenases) NAD+ NADH • Pyridoxal (vit. B6) • in meat, vegetables, grain products • function: the coenzyme in the amino acid metabolism

  7. Nucleotide bases derived from pyrimidine • in nucleic acids Cytosine Uracil Thymine (in both RNA and DNA) (in RNA) (in DNA) • a nucleic acid base is N-glycosidically linked to ribose or 2-deoxyribose • the sugar is esterified with phosphoric acid

  8. Nucleotide bases derived from purine • in nucleic acids , ATP, NADP, FAD, CoA • degradation of purine nucleotides → uric acid (excreted) Guanine Adenine Uric acid (in both RNA and DNA) (in both RNA and DNA) anhydride bonds an ester bond • the most important form of chemical energy in cells ATP

  9. Folic acid • in fresh green vegetables, liver • its deficiency (megaloblastic anemia) • function: coenzyme in C1 metabolism (nucleotide biosynthesis) • Riboflavin • in milk, eggs • function: in the coenzymes FMN and FAD (oxidation and reduction) riboflavin FAD FADH2

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