Biomedical Engineering Reference
In-Depth Information
TABLE 8.2
Cofactors (Metal Ions) and Coenzymes of Some Enzymes
Cofactors
Coenzymes
Entity transferred
Zn
2+
Nicotinamide adenine dinucleotide
Hydrogen atoms
Alcohol dehydrogenase
Nicotinamide adenine dinucleotide
phosphate
Hydrogen atoms
Carbonic anhydrase
Carboxypeptidase
Flavin mononucleotide
Hydrogen atoms
Mg
2+
Flavin adenine dinucleotide
Hydrogen atoms
Phosphohydrolases
Phosphotransferases
Coenzyme Q
Hydrogen atoms
Mn
2+
Thiamin pyrophosphate
Aldehydes
Arginase
Phosphotransferases
Coenzyme A
Acyl groups
Fe
2+
or Fe
3+
Lipoamide
Acyl groups
Cytochromes
Peroxidase
Cobamide coenzyme
Alkyl groups
Catalase
Biocytin
Carbon dioxide
Ferrodoxin
Pyridoxal phosphate
Amino groups
Cu
2+
or Cu
+
Tyrosinase
Cytochrome oxidase
Tetrahydrofolate coenzyme
Methyl, methylene,
formyl, or formino
groups
K
+
Pyruvate kinase (also require Mg
2+
)
Na
2+
Plasma membrane ATPase (also
requires K
+
and Mg
2+
)
8.2.2. Mechanistic Models for Simple Enzyme Kinetics
Both the pseudosteady-state approximation and the assumption of rapid equilibrium
share the same few initial steps in deriving a rate expression for the mechanism in Eqn
(8.3)
, where the rate of product formation
r
p
¼ r
2
¼ K
2
½
ES
(8.3)
The rate constant k
2
is often denoted as k
cat
in the biological literature. The rate of formation of
the ES complex is
r
ES
¼ r
1
r
2
¼ k
1
½
E
½
S
k
1
½
ES
k
2
½
ES
(8.4)
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