Studies on the crystalline lens XII. Turnover of glycine and glutamic acid in glutathione and ophthalmic acid in the rabbit

¹ Kresge Eye Institute of Wayne State University, School of Medicine Detroit, Mich.
² Kresge Eye Institute of Wayne State University, School of Medicine Detroit, Mich.; Clinique Ophtalmologique, Université de Strasbourg, Strasbourg, France

The rates of incorporation of ¹⁴C-labeled glycine and glutamic acid into glutathione and ophthalmic acid have been determined in cultured rabbit lenses. The average turnover rate of glycine and glutamic acid in glutathione, and of glutamic acid in ophthalmic acid was found to be 1.8 per cent per hour throughout the 24 hour period of culture; the incorporation of glycine in ophthalmic acid also occurred at this rate for the first 9 hours but appeared to decrease thereafter. While the possibility of exchange reactions cannot be ruled out, the similarity of the rates of turnover of both amino acids in each peptide strongly suggest that glutathione and ophthalmic acid are continually being broken down and resynthesized in the lens. The rate of formation of glutathione and ophthalmic acid, assuming incorporation of amino acids represents synthesis, is 21.6 and 0.52 µmoles per 100 Gm. lens per hour, respectively