Chemistry Reference
In-Depth Information
10
12
10
11
10
10
10
9
10
8
10
7
O
2
-.
1
O
2
O
3
˙
OH
10
6
10
5
10
4
10
3
10
2
10
1
10
0
10
-1
Cys
Met
Trp
Tyr
His
Phe
Figure 4.33.
comparison of the reactivity of some amino acids with ROS (data were
taken from Tables 4.6, 4.10, and 4.11 and from Bielski and Shiue [48] for superoxide
reactivity).
and the diffuse distance of ROS, as well as the location of residues in proteins
or enzymes which control the efficiency of inactivation. For example,
O
•−
has
a longer half-time than the
•
OH radical and therefore can diffuse at great
distances to react with amino acid residues, even in locations including the
protein's active site [4]. It has been determined that
O
•−
is efficient in the
inactivation of protein A as is a
•
OH radical [357]. The rate constants of the
reactions of glyceraldehydes-3-phosphate dehydrogenase (gAPDH) and
alcohol dehydrogenase (ADH) with
O
•−
are at least three orders of magnitude
lower than with the
•
OH radical [25, 277], but effectiveness results showed the
inactivation of gAPDH and ADH by
O
•−
was only 2.4 and 2.8 times smaller,
respectively, compared with the
•
OH radical [4]. The lifetime and diffusion
distance of intracellular
1
O
2
may also be significant in
1
O
2
-mediated cell death
[157]. The conformation and structure of proteins
in vivo
would determine
accessibility of the amino acid residues to ROS for their modifications. com-
parative studies on proteins
in vivo
are very limited, and further studies are
needed to establish the general criteria between the reactivity of ROS and the
protein structure.
A comparison of the products obtained in the oxidation of Met, Trp, His,
and Tyr in their free forms by different ROS is presented in Table 4.14 [358].
1
O
2
produced a sulfonate derivative in reaction with Met. However, a different
product, hydroxymethione, was produced in reaction with
•
OH under similar
conditions. Both NFK and hydroxyl-NFK were the products from the oxida-
tion of Trp. The oxidation of His resulted in a number of compounds. A group
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