Coenzymes and Vitamins

C483 Spring 2013

1. Unlike NADH and NADPH, FAD and FADH2 A) donate one electron at a time.B) donate one or two electrons at a time.C) do not become positively charged.D) A and C. E) B and C.

2. Which coenzyme is likely involved in the reaction shown below?A) TPP. B) Biotin. C) Coenzyme A. D) FMN.

3. Pyridoxal phosphate is involved in which type of reaction? A) Oxidation of pyruvate. B) Production of new amino acids by transamination. C) Phosphate-transfer to produce ATP from ADP. D) methyl transfer

4. What kind of reaction is most important for the reactive center of lipoamide?

A) Oxidation of a carbonyl group.B) Reduction of a disulfide bond.C) Formation of a Schiff base.D) Transamination

5. THF is involved in transfer of carbon in what oxidation state?A) methylB) methyleneC) formylD) carboxylE) more than one of the above

Terminology

Vitamins and Minerals

Vitamins

Water and lipid solubility

Objectives

• Know selected structures (abbreviated structures)

• Recognize types of reactions and relate to appropriate cofactor

• Selected major mechanisms

1. Phosphorylation and Energy Transfer

• ATP• Phosphate transfer– Hydrolysis

• Reaction:

2. Redox Reactions

• NADH/NAD+ (NADPH/NADP+)• Know abbreviated structure

Reaction of NADH/NAD+

• 2 electron transfer• DH• cosubstrate• Know general

oxidation and reduction

Enzyme: Lactate DH

Flavins

• FAD/FADH2

• FMN/FMNH2

• Recognize abbreviated structure

Reactions of Flavins

• 1 or 2 electron transfer

• Prosthetic group• No mechanisms

3. Acyl Carrier/Transfer

• Coenzyme A• Pantothenate is vitamin B5

• Know abbreviated Acetyl CoA structure

Reactions of Acetyl CoA

• Thioester is a nucleophile• High energy linkage• Review Nucleophilic Acyl substitution• Reaction:

Lipoamide

• Technically, not a vitamin• Connected to protein—recognize abbreviated• Electrophilic acyl carrier—see mechanism• Redox reaction

4. Decarboxylation

• Thiamine Pyrophosphate (TPP or TDP)

• Know abbreviated structure

Reactions

• Decarboxylases• a-keto acids• Know initial phase of reaction:

5. Reactions of Amino Acids

• Pyridoxal phosphate (B6)• Know abbreviated structure

Schiff Base formation• Covalent imine formation with lysine• No mechanism—but structure of pdt– Bad mechanism given in book!

Reactions

• Decarboxylation, Racemization, Transamination, Others

One Carbon Transfers

• Recognize coenzyme• Know oxidation level of transfer

Coenzyme Carbon group

S-adenosyl methionine (SAM) methyl

Cobalamine (B-12) Methyl (and rearrangements)

Tetrahydrofolate (THF) Methyl, methylene, formyl

Biotin Carboxy

SAM

B-12

THF

Biotin

Answers

1. E2. A3. B4. B5. E