University:
Boston University
Course:
CAS BI 107 | Biology 1
Academic year:

2021
Views:

497

Pages:

10
Author:

Pierce Valdez

Vitamins & Cofactors Vitamins & Cofactors Vitamins Ø Definition: essential nutrients required in the diet Ø Different vitamins for different species e.g., for rats & mice ascorbate is not a vitamin E. coli do not have any vitamins Ø Vitamins are classified as water soluble or fat soluble Cofactors/Coenzymes Ø Definition: low Mr molecules that act as carriers or give special functionality to enzymes Ø Many coenzymes have vitamin molecules as their basis Need to know: name, abbreviation, recognize structure, role in chemistry 1 Vitamins & Cofactors Reaction mediated Human Deficiency Disease Beriberi Pellagra ① ② Acyl-group transfer Re-dox ③ Re-dox – ④ ⑤ Acyl-group transfer Amino-group transfer dermatitis ⑥ Alkylation Pernicious anemia ⑦ ⑧ ⑨ Carboxylation Acyl-group transfer C1-group transfer Megaloblastic anemia Re-dox Scurvy 10 Ascorbic acid (vitamin C) Fat-soluble ① Ascorbate Retinal – – – Night blindness ② Rickets – Hemorrhage ③ ④ Vitamins & Cofactors ① Vitamin B1 Acyl-group transfer Thiazole ring Vitamin H In 1911, Casamir Funk realized that this “amine” was “vital” for life. He coined the term “vital-amine,” which eventually was shortened to the word, “vitamin.” Coenzyme H 2 Vitamins & Cofactors ① Vitamin B1 Acyl-group transfer Thiazole ring Vitamin H In 1911, Casamir Funk realized that this “amine” was “vital” for life. He coined the term “vital-amine,” which eventually was shortened to the word, “vitamin.” Coenzyme H Vitamins & Cofactors ② Vitamin B3 Re-dox (aka Niacin) Vitamin Pro-S Pro-R Coenzyme Nicotinamide adenine dinucleotide Hydride (H:–) Nicotinamide • These are commonly called pyridine nucleotides. • They can dissociate from the enzyme after the reaction. • In a typical biological oxidation reaction, hydride from an alcohol is transferred to NAD+, giving NADH. • Renamed niacin for nicotinic acid and vitamin 3 Vitamins & Cofactors ② Vitamin B3 Re-dox (aka Niacin) Vitamin Pro-S Pro-R Coenzyme Nicotinamide adenine dinucleotide Hydride (H:–) Nicotinamide • These are commonly called pyridine nucleotides. • They can dissociate from the enzyme after the reaction. • In a typical biological oxidation reaction, hydride from an alcohol is transferred to NAD+, giving NADH. • Renamed niacin for nicotinic acid and vitamin Vitamins & Cofactors ③ Vitamin B2 (aka riboflavin) Coenzymes Re-dox • Flavin Cofactors Allow Single Electron Transfers • Permits the use of molecular oxygen as an ultimate electron acceptor • flavin-dependent oxidases • Flavin cofactors are tightly bound to proteins. Vitamin H lmax = 570 nm lmax =Isoalloxazine 450 nm Ring 4 Vitamins & Cofactors ③ Vitamin B2 (aka riboflavin) Re-dox • Flavin Cofactors Allow Single Electron Transfers • Permits the use of molecular oxygen as an ultimate electron acceptor Coenzymes • flavin-dependent oxidases Vitamin • Flavin cofactors are tightly bound to proteins. lmax = 570 nm lmax = 450 nm Vitamins & Cofactors ④ Pantothenic acid Acyl-group transfer Vitamin –O Coenzyme A H OH 5 Vitamins & Cofactors ④ Pantothenic acid Acyl-group transfer Vitamin Coenzyme A Vitamins & Cofactors ⑤ Vitamin B6 Amino-group transfer Vitamin Coenzyme O = O O-P| O – – Pyridoxal 5-phosphate (PLP) 6 Vitamins & Cofactors ⑥ Vitamin B12 Alkylation Vitamin Cobalt ion Dimethylbenzimidazole Coenzyme Vitamins & Cofactors ⑦ Biotin Vitamin Carboxylations Used to attach carboxyl group (–CO2–) Tightly binds Avidin and streptavidin (Kd=~10-15); used in biotechnology Used to attach to enzyme (Lys) Coenzyme (covalent) Carboxylbiotin R 7 Vitamins & Cofactors ⑧ Lipoic Acid Vitamin Acyl-group transfer Coenzyme (covalent) Vitamins & Cofactors ⑧ Lipoic Acid Vitamin Acyl-group transfer Coenzyme (covalent) 8 Vitamins & Cofactors ⑨Folic Acid (aka Vitamin B9) One-carbon transfer •Folate deficiency: • During – Diarrhea pregnancy: fetal – Depression neural tube – Confusion defects – Anemia Vitamin Coenzyme 8 2 7 1 3 6 4 5 NADPH + H+ NADPH + H+ ⇌ ⇌ 5 10 Tetrahydrofolate (THF) Vitamins & Cofactors 10 Ascorbic Acid (aka Vitamin C) Re-dox Vitamin Coenzyme 9 Vitamins & Cofactors 10 Ascorbic Acid (aka Vitamin C) Re-dox Vitamin Coenzyme 10

Vitamins and Cofactors

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