Metabolism of amino acids in the lens

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Abstract
Radioactive glycine was incorporated into the proteins of the cortex of intact ox lens to a much greater extent than into those of the nucleus of the lens. The specific activities of the [alpha]-crystallin and [beta]-crystallin fractions were comparable. The kinetics of the incorporation of mixed radioactive amino acids into ox lens protein lead to a calculated value of 0.06 mg/hr for the rate of protein synthesis; growth contributes only 0.01 mg/hr to this value. These values indicate that protein turnover occurs in the lens. The incorporation of uniformly labelled L-valine into the proteins of calf lens was inhibited by puromycin; the inhibition did not lead to the accumulation of appreciable amounts of radioactive peptides. Catabolism of valine by the lens gave glutamate, glutathione and several unidentified products. Glycine was converted in the lens into glutathione, ophthalmic acid, norophthalmic acid, serine, lactate, adenosine triphosphate and several unidentified products; the extent of incorporation of radioactivity into glutathione was high.