Biochemical Cofactors

BIOCHEMICAL COFACTORS

Nicotinamide-Adenine-Dinucleotide (NAD)

Nicotinamide-Adenine-Dinucleotide Phosphate (NADP)

Building blocks: O 5' NH HO 7 2 4 6 O 1' N 5 5 OH N 1 3 NH2 4' 8 3' 2' 2 6 N 2 9 N 4 N 1 HO OH H 3 Nicotinic Acid D-ribose Adenine

Adenine + ribose ∅ adenosine (a nucleoside)

NAD+ NADH (reduced form of NAD+) NH O 2 N N O H H H N O O 2 C O P O P O N N H2N N OH OH O OH HO N O HO OH R

Isolation: Euler, 1931 Characterization: Euler, Schenk, Karrer, 1942 Synthesis: Todd, Hughes, 1957 Eo (pH = 7): -0.32 V Function: Cofactor for oxidoreductases in the respiratory chain

NH O 2 N N H N O O + 2 NADP O P O P O N N N OH OH O OH HO O O HO O P OH OH Isolation: Warburg, Christian, 1934 Characterization: Warburg, Christian, 1934 Synthesis: Todd, 1957 Eo (pH = 7): -0.32 V Function: Redox-cofactor for many biosynthetic processes 2

Flavin-Mono-Nucleotide (FMN) and Flavin-Adenine-Dinucleotide (FAD)

Building blocks: NH2 N O CH2OH N 5 10 H C 6 N 4a 4 3 H C OH 3 NH HO N N 2 H C OH O H3C 7 9 N N O H C OH 8 H 1 CH OH 2 HO OH 6,7-Dimethyl-isoalloxazine Ribitol Adenosine

FMN FMNH2

O O H H3C N CH N NH 3 NH

H3C N N O CH3 N N O H CH2 R H C OH H C OH H C OH O

CH2 O P OH OH

Riboflavin (Vitamin B2)

Isolation (vitamin): György, Kuhn, Wagner-Jauregg, 1933 Characterization: Thorell, 1935 Synthesis: Kuhn, Karrer, 1935 Eo (pH = 7): -0.21 V Function: Proton transfer, electron transfer

O H C N 3 NH FAD H3C N N O

CH2 H C OH NH2 H C OH N N H C OH O O N CH2 O P O P O N OH OH O

HO OH

Isolation: Warburg, Christian, 1938 Characterization: Todd, 1954 Function: Cofactor for oxidoreductases in the respiratory chain 3

Heme

N N FeIII N N

CO2H CO2H

Isolation: Bertin-Sans, de Moitesier, 1892 Synthesis: Fischer-Orth, 1937 Function: Electron transport; Hydroxylation; Epoxidation (detoxification of xenobiotics)

Ubiquinone (Coenzyme Q)

CH3

H n n = 6 - 10 O CH3

Isolation: Morton, Green, 1958 Characterization: Morton, Green, 1958 Synthesis: Merck, 1960 Eo (pH 7): + 0.10 V Function: Electron transfer (to cytochrome b)

Vitamin K O

CH3

H 4 O CH3

Isolation: Dam, 1939 Characterization: Dam, 1929 Synthesis: Fieser, 1939 Function: Carboxylation of proteins involved in blood coagulation 4

Thiamine pyrophosphate (Vitamin B1)

NH 2 + CH3 N N O O O P O P OH H3C N S OH OH

Isolation: Lohman, Schuster, 1943 Characterization: Lohman, Schuster, 1943 Function: Umpolung of carbonyl groups, for example in the decarboxylation of α-ketoacids, formation of acyloins, andtransketolase reactions

Pyridoxal phosphate (PLP) and Pyridoxamine phosphate (PMP)

O H NH2 C O HO O HO O P OH O P OH OH OH H3C N H3C N

PLP PMP

Isolation: Sale, Epps, 1943 Characterization: Baddiley, Mathions, 1952 Function: Catalyzes ca. 40 biochemical reactions, including racemization of amino acids, transaminations, decarboxylation of amino acids, α,β-eliminations (e.g. serine ∅ pyruvate), β,γ-eliminations (e.g. homocysteine ∅ ketobutyric acid), synthesis of tryptophanm desaldolization of serine (∅ glycine)

S-Adenosylmethionine (SAM) NH2 N N H3C N N H2N S O COOH HO OH

Isolation: Cantoni, 1952 Characterization: Cantoni, 1952 Synthesis: Baddiley, Jamieson, 1954 Function: Biological methylation reagent (for O-, S-, N- and C-acceptors)

Coenzyme A (CoA or CoA-SH) NH2 N N O O O O N HS O P O P O N N N O H H OH OH OH O OH Pantothenic acid O P OH OH Pantethine

Isolation: Lipmann, 1947 Characterization: Lipmann, Snell, Baddiley, Lynen, 1948-1953 Synthesis: Khorana, 1961 Eo (pH 7): -0.29 V Function: Acylation of the thiol yields the so-called "active form" of carboxylic acids: RCO-S-CoA (an S-acyl-CoA-ester). Such esters serve, e.g., as substrates for carboxylations, α- condensations, reductions to aldehydes, and transacylations.

Lipoic Acid (Thioctic Acid) and Dihydrolipoic Acid

COOH COOH

S S SH SH

Isolation: Reed, Gunsalus, 1953 (10 ton liver ∅ 30 mg) Characterization: Reed, 1955 Synthesis: Reed, 1955 Eo (pH 7): -0.29 V Function: Oxidative decarboxylation of α-ketoacids (Dihydrolipoic acid: acyl group transfer)

Tetrahydrofolic Acid (FH4) and Analogues

Building blocks: O COOH H 4 5 H N H N CH3 2 3 HN 6 CH H2N COOH 2 7 CH H2N 2 N 8 N 2 1 H COOH

2-amino-4-oxo-6-methyl- p-Aminobenzoic acid Glutamic acid 5,6,7,8-tetrahydropteridine

FH4

O H O COOH N 5 10 Pteroyl-L-glutamic acid = folic acid = vitamin HN NH NH H Bc CH2 H2N N N 10 H CH2 N -Formyl-pteroic acid = rhizopterin 5 COOH N -Formyl-FH4 = leucovorin

Tetrahydropteroic acide

Isolation: Pfiffer, 1943 (Folic acid) Characterization: Hutchings, 1948 Synthesis: Hutchings, 1948 Function: C1-transfer at the formic acid, formaldehyde and methanol oxidation states Occurrence: e.g. in spinach leaves 5 pKa (N ): 4.8 10 pKa (N ): -1.25

Biotin (Vitamin H) O 6 4 HN 5 NH

7 3 2 8 1 COOH S

Isolation: Kögl, 1935 (250 kg egg yolk ∅ 1 mg) Characterization: Du Vigneaud, 1942 Synthesis: Merck, 1943 Function: Carboxylations in fatty acid biosynthesis; Transcarboxylations

The active carboxylation agent was identified by Lynen in 1959 as (enzyme-bound) N6-carboxy-biotin 7

Vitamin-B12-Coenzyme

H2NOC H3C H3C CONH2 CONH2 H2NOC H C 3 N R N Cobirinic acid- H3C Co N N hexamide CH3 H NOC 2 CH3 CH O CH3 3 CONH2 H NH O N H3C O P O HO CH 3 5,6-Dimethyl- OH N

O CH3 benzimidizole HO

Cyanocobolamine (vitamin B12), R = CN Aquocobalamine, R = H2O Coenzyme B12, R = 5'-Deoxyadenosyl-

Isolation (vitamin): Smith, Folkers, 1948 Crystal structure: Crowfoot-Hodgkin, 1957 Synthesis: Eschenmoser, Woodward, 1972

Coenzyme B12

HO OH Isolation: Barker, 1958 Function: Catalyzes rearrangements like O N N R CH 1 H 2 N N R2 C C R3 Co NH 2 H H

Example:

H2N COOH H COOH H NH2 !-Lysine- NH2 NH2 isomerase

Aquo-cobalamine involved in biosynthesis of methionine, biosynthesis of acetate, formation of methane 8

Some biologically important redox potentials