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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