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Myopia or shortsightedness is the most common human eye disease affecting 30% of the
world population. Genetic and environmental factors are implicated in the onset of myopia.
Environmental causes include mechanical factors, oxidative stress, nutritional factors etc.
Humans vary in their ability to metabolize endogenous and exogenous compounds.
Glutathione-S-Transferase is one of the enzyme systems which can detoxify several
carcinogens and cytotoxic drugs. Oxidation-reduction mechanisms have special importance
in many tissues, including the eye lens (Augusteyn, 1981; Spector, 1984; and Berman, 1991).
Enzymes such as Catalase, Superoxide dismutase, Glutathione peroxidase, and Glutathione S-Transferase (GST) are thought to be important in the protection of the eye from oxidative
damage (Spector, 1984; and Huang et al., 1993).
GSTs (EC 2.5.1.18) are a group of dimeric enzymes catalyzing the conjugation of reduced
glutathione (GSH) with a broad spectrum of electrophiles and thus involved in the
detoxification processes (Mannervik and Danielson, 1988). Hence, it plays a significant role
in detoxification of Xenobiotics and other endogenous toxic compounds and for the protection
of tissues from oxidative damage. The members of the GST gene family are placed in the
multigene classes of Alpha, Mu, Pi, Kappa, Theta and Zeta on the basis of sequence identity
(Meyer et al., 1991; Mannervik et al., 1992; and Board et al., 1997). Among these classes
of GSTs, genetic polymorphism is well described for the GST M1, GST M3, GST T1, GST
P1 and GST Z1 loci. There are three alleles at the GST M1 locus: GST M1*0, GST M1*A,
and GST M1*B. The GST M1*0 is a deletion, and homozygotes for this gene express neither
mRNA nor protein. |
