Download Cofactors and Coenzymes

Cofactors and
Coenzymes
Cofactors
• Groups or molecules (other than amino
acid residues) which are important to
catalysis
– Metals
– Coenzymes
• If tightly bound, it is called a prosthetic
group
• Enzyme without prosthetic group
(cofactor)
– Apoenzyme
• Enzyme with prosthetic group (cofactor)
– Holoenzyme
Catalysis by Coenzymes
Some common
coenzymes Transfers
• Oxidation/Reduction
– Nicotinamide Adenine
Dinucleotide (NAD+)
– Flavin Adenine
Dinucleotide (FAD)
Hydride ion (H-)
Electrons
Catalysis by Coenzymes
Some common
coenzymes
• One carbon metabolism
– Biotin
– Tetrahydrofolate
Transfers
CO2
One carbon
groups
O
C
H
to
CH3
Catalysis by Coenzymes
Some common
Transfers
coenzymes
• Acyl groups and others Acyl groups
– Coenzyme A
Acyl groups
– Lipoic acid
Aldehydes
– Thiamine pyrophosphate
Amino groups
– Pyridoxal phosphate
and amines
– 5’-DeoxyadenosylAlkyl groups
cobalamin
Vitamin Derived Coenzymes
Derived Deficiency
Coenzyme
from
causes
NAD
Niacin
Pellagra
FAD
Riboflavin Dermatitis
(B2)
Biocytin
Biotin
Seborrhea
(skin)
Tetrahydro- Folate
Varies
folate
Vitamin Derived Coenzymes
Coenzyme A
Pantothenate Fatigue
+ others
Irritability
Thiamine
Thiamin (B Beriberi
pyrophosphate
Pyrodoxal
phosphate
Pyridoxine
(B6)
5’-Deoxyaden- Vitamin B12
osylcobalamin
Varies
Pernicious
Anemia
Examples of Coenzyme Catalysis
Uncatalyzed reaction
H
R
C
O
H
C
R
O
NH3
CO 2
C
NH 3
H
H
R
C
NH3
H
Examples of Coenzyme Catalysis
Catalysis with pyridoxal phosphate (Vitamin B6 derivative)
H
R
C
H
O
C
NH3
R
O
NH
H 2O
+
X
CH
O
X
X
X
X
C
HC
O
X
C
O
N
H
X
N
H
X
Schiff Base
Examples of Coenzyme Catalysis
H
R
C
NH
O
H
C
R
O
X
R
X
CO2
X
X
N
H
C
NH
HC
HC
X
N
H
C
NH
HC
X
H
X
X
X
X
X
N
H
X
Examples of Coenzyme Catalysis
H
R
C
R
NH
X
H H 2O
CH
X X
N
H
R
C
C
H
NH2
NH
CH
X
H
H
X X
CH
X
N
H
O
H
X
X
X
X
N
H
X
Examples of Coenzyme Catalysis
Nicotinamide adenine dinucleotide and alcohol dehydrogenase
O
C
NH2
-
N
O
H2C
NH2
OH OH
O
O
O
P O
P O
O
O
NAD+
H
[H ]
NH2
N
N
N
H
R
NADH
OH OH
O
C
N
N
CH2
O
H
Examples of Coenzyme Catalysis
R
H
Zn2+
H
O
N
C
H
O
C
CH3
H2N
H
H
NAD
H
C
CH 3
OH