Biochemistry of Minerals

1. Biochemistry of Minerals C H N O S P Na K Ca Mg Cl Biological forms of minerals in living systems Fe Zn Cu Mn Se Co V Si As Mo I Br F

2. Characteristics of Biochemical Ion Complexes Na+, K+ Mg2+,Ca2+ Zn2+, Ni2+ Fe, Cu, Co, Mo, Mn After Frausto de Silva and Williams

3. Glucose Hemoglobin Na+ Fe2+ intestine mitochondria O2 Glucose H2O liver PO43- Mg2+ Fe2+ Mn2+ K+ Mg2+ Ca2+ Cu2+ PO43-

4. Inorganic Enzyme Cofactors (one-third of all enzymes require a metal ion for catalytic function)

5. Metalloenzymes vs Metal Activated Enzymes Metal Activated Metalloenzyme 1. Metal in equilibrium Metal firmly affixed to protein 2. Activated by adding metal ion Adding metal has minimal effect 3. Metal lost on isolation Metal stays bound, removable by chelators 4. No stoichiometry with protein Integral number per protein 5. Electrostatic bonding Coordinate covalent bonding 6. Multiple metal binding sites Limited number, generally one 7. Binding sites, angles irregular Binding sites exhibit specific geometry • Mostly group IA and IIA metals • Na+, K+, Mg2+. Ca2+ Mostly 3d transition metals Zn2+, Fe2+. Cu2+, Co2+

6. Examples of Metalloenzymes Zinc (over 300) Manganese Arginase Water splitting enzyme Pyruvate carboxylase Dehydrogenases RNA, DNA polymerase Carbonic anhydrase Carboxypeptidase Amino peptidase Cobalt (with B12) Methylmalonyl CoA mutase Homocysteine transmethylase Copper Superoxide dismutase Tyrosinase Cytochrome oxidase (with Fe) Lysyl oxidase Peptide amidating Dopamine beta hydroxylase Molybdenum Nitrogenase Xanthine oxidase Calcium Iron Thermolysin Ribonucleotide reductase Cytochrome oxidase (with Cu) Nickel Urease

7. Quick Overview of Mineral Functions Zn2+ Na+, K+, Cl- Osmotic control Electrolyte equilibria Ion currents Gated channels Lewis acid Enzyme cofactor Protein structure Hormone activator Neurotransmitter Genetic expression regulator Mg2+ Fe2+, Fe3+ Phosphate metabolism Heme iron Electron transport Oxygen activator Oxygen carrier Ca2+ Muscle contraction Cell signaling Enzyme cofactor Blood clotting Mineralization Morphogenesis Gene regualtion Cu+, Cu2+ Enzyme cofactor Oxygen carrier Oxygen activator Iron metabolism

8. Quick Overview (cont.) Cr3+ Se Insulin mimetic Glucose metabolism Redox reactions Antioxidant Mo2+ Mn2+ Enzyme cofactor Nitrogen activator Enzyme cofactor (limited) Ni2+ HPO4=, Si Coenzyme Remnant of early life Acid-base non metals Biomineralization Co3+ Vitamin b12

9. Examples of Metalloproteins Function 1. Metallothionein Cu, Zn, Cd storage, heavy metal buffer 2. Ferritin Iron storage, iron buffer 3. Calmodulin Ca binding, allosteric regulator 4. Transferrin Iron transport Selenium transport 5. Selenoprotein W 6. Calbindin Calcium transport

10. Biomineralization Calcium and phosphate Bones and Teeth

11. Cross section through trebecular and cortical bone revealing the internal architecture surrounded by marrow tissue. Cortical bone with Halversion system (a series of channels supplying nutrients). Black dots are osteocytes Leg bone of a horse showing the trebecular (spongy) bone and the cortical (solid) bone. This bone is able to withstand forces generated by this 1,500 lb animal Trebecular bone of the lower spine. Changes with aging.

12. Demineralized bone: Shown is he organic matrix consisting mostly of collagen upon which the bone crystals are laid.

13. Hydroxyapatite (crystal structure) Ca10(PO4)6 OH2 Ca P O H

14. Zinc Function • 300 enzymes require zinc • DNA, RNA polymerases • numerous hormones require zinc • insulin • EGF • transcription factors (zinc finger proteins) • membrane stability • myelination • skeletal development

15. Metal Ions in Catalysis- One third of all enzymes require a metal ion for catalysis

16. His His O O .. His –Zn2+ His –Zn2+ O O C + C O H H O His His His O .. His –Zn2+ + H+ + H O C O O H His Bicarbonate Zn 2+Polarizes H2O, making it a better nucleophile H2O Displaces HCO3-

17. Biochemical Iron • Hemoglobin- oxygen carrier in the blood • Myoglobin- O2 carrier in cells (mostly in muscle) • Cytochromes- electron carriers in membranes • Catalase- enzyme that destroys H2O2 (hydrogen peroxide) • Cytochrome oxidase- electron transport, ATP synthesis in mitochondria • Cytochrome P450- detoxifying enzyme • Nitrogenase- nitrogen fixation • Ferritin- iron storage in cells, plasma • Transferrin- iron transport in blood • Iron-sulfur electron proteins- electron carriers • Tyrosine and phenylalanine hydroxylase- enzymes that synthesizes L-DOPA and tyrosine, respectively • Ribonucleotide reductase- enzyme that forms deoxyribose from ribose

18. Function • Oxygen Transport & Storage • Hemoglobin • Myoglobin • Electron Transport & Energy Metabolism • Cytochromes • Fe-S proteins • Substrate Oxidation & Reduction – Iron dependent enzyme- • Ribonucleotide reductase • Amino acid oxidases • Fatty acid desaturases • Nitric oxide synthetase • Peroxidases All use O2 as a substrate

19. Examples of Iron-dependent Enzymes Aldehyde Oxidase R-CHO + O2 RCOOH + H-O-O-H Tryptophan 5-monooxygenase L-tyrptophan + BH4 + O2 5 OH L-tryptophan + BH2 + H2O Fatty Acid desaturase Stearoyl-CoA + NADH + H+ + O2 Oleoyl-CoA + NAD+ + 2H2O Peroxidase 2H2O2 2H2O + O2 (O2 is either incorporated into the product or reduced by electrons)

21. Electron Transport Complexes • Membranes bound heme proteins or “cytochromes” • Iron-Sulfur proteins..high reducing potential • Mobile electron carriers • Coenzyme Q • Cytochrome c

22. Transport Mechanism .. .. .. .. .. .. .. .. Cyt a+a3 (Fe2+) Cyt b (Fe3+) Cyt c1 (Fe2+) Cyt c (Fe3+) FMN CoQH2 O2 NAD+ Cyt b (Fe2+) Cyt c1 (Fe3+) Cyt c (Fe2+) Cyt a+a3 (Fe3+) H2O FMNH2 CoQ Reduced Oxidized A bucket-brigade NADH + 0.82 volts -0.32 volts

25. Electron Transfer “Pump” Dinitrogenase M o A c t i v a t e d 0 . 4 0 M o - H - F d - e R M o - H N = N H - 0 . 2 9 F d R e H - M o - H A T P A D P H H 2 Dinitrogenase Reductase H - M o = N = N - F d - e R M o - F d R e A T P A D P H - M o = N - N H 2 e + H+ - F d - e R N H 3 e + H+ - F d R e A T P A D P N H N M o = 3 e + H+ Iron and Molybdenum in Nitrogenase Fe N2 + 3H2 2NH3