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Isoenzymes. R ole of cofactors and coenzyme vitamins in the catalytic action of enzymes.

Isoenzymes. R ole of cofactors and coenzyme vitamins in the catalytic action of enzymes. Coenzymes. Coenzymes act as group-transfer reagents Hydrogen, electrons, or groups of atoms can be transferred. Coenzyme classification.

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Isoenzymes. R ole of cofactors and coenzyme vitamins in the catalytic action of enzymes.

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  1. Isoenzymes. Role of cofactors and coenzyme vitamins in the catalytic action of enzymes.

  2. Coenzymes • Coenzymes act as group-transfer reagents • Hydrogen, electrons, or groups of atoms can be transferred Coenzyme classification • (1) Metabolite coenzymes - synthesized from common metabolites • Vitamin-derived coenzymes - derivatives of vitamins • Vitamins cannot be synthesized by mammals, but must be obtained as nutrients

  3. Examples of metabolite coenzymes ATP can donate phosphoryl group ATP S-adenosylmethionine donates methyl groups in many biosynthesis reactions S-adenosylmethionine

  4. 5,6,7,8 - Tetrahydrobiopterin Cofactor of nitric oxide synthase

  5. Vitamin-Derived Coenzymes • Vitamins are required for coenzyme synthesis and must be obtained from nutrients • Most vitamins must be enzymatically transformed to the coenzyme • Deficit of vitamin and as result correspondent coenzyme results in the disease

  6. NAD+ and NADP+ • Nicotinic acid (niacin) an nicotinamide are precursor of NAD and NADP • Lack of niacin causes the disease pellagra NAD and NADP are coenzymes for dehydro-genases

  7. FAD and FMN • Flavin adenine dinucleotide (FAD) and Flavin mononucleotide(FMN) are derived from riboflavin (Vit B2) • Flavin coenzymes are involved in oxidation-reduction reactions FMN (black), FAD (black/blue)

  8. Thiamine Pyrophosphate (TPP) • TPP is a derivative of thiamine (Vit B1) • TPP participates in reactions of: (1) Oxidative decarboxylation(2) Transketo-lase enzyme reactions

  9. Pyridoxal Phosphate (PLP) • PLP is derived from Vit B6 family of vitamins • PLP is a coenzyme for enzymes catalyzing reactions involving amino acid metabolism (isomerizations, decarboxylations, transamination)

  10. Enzymes active sites Substrate usually is relatively small molecule Enzyme is large protein molecule Therefore substrate binds to specific area on the enzyme Active site – specific region in the enzyme to which substrate molecule is bound

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