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) methyl
B) methylene
C) formyl
D) carboxyl
E) 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.
2.
3.
4.
5.
E
A
B
B
E