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—We appreciate Dr Bryant's careful perusal of our data concerning GK and GPUT activity in presenile cataract formation. However, the tabulated data Dr Bryant refers to are in Table 2 rather than Table 1.Regarding the absence of a correlation between GK activity and GPUT activity, we believe it questionable whether one can compare in vitro RBC activity of an enzyme under artificial conditions (vast excess of substrate, dilution or loss of possible inhibitors, and others) with normal biological activity of the same enzyme in cells of the body. Both GK and GPUT are completely separate enzymes, and a low level of one should not lead one to expect "disuse atrophy" of the other. We are unaware of any such known relationship between successive enzymes in a metabolic pathway.Dr Bryant found a "relationship" between GK and GPUT in the black patients listed in our Table. Table 2
Skalka H, Prchal J. Cataract Formation-Reply. Arch Ophthalmol. 1980;98(8):1487. doi:10.1001/archopht.1980.01020040339026