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U.C. Yadav, A.B. M. Reddy, R. Tammali, K.V. Ramana, S.K. Srivastava; Distribution of Fiber Cell Globulizing Aminopeptidase (FCGAP) in Bovine and Rat Ocular Tissues: Role in Cataractogenesis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4323.
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We have shown that rat and bovine lens have a unique Ca2+–independent aminopeptidase (FCGAP) which is immunologically distinct from leucine aminopeptidase and similar to GST. The purpose of this study was to determine the distribution of FCGAP and GST in ocular tissues and to investigate their involvement in Ca2+–induced globulization of isolated rat lens fiber cells.
GST activity was determined using 1–chloro–2, 4–dinitrobenzene (CDNB) as a substrate and FCGAP activity was determined by following the increase in fluoroscence of cleavage product of BOC–Leu–Met–CMAC–SG. Fiber cell globulization was determined as described, (Chandra D et al, IOVS. 2002; 43: 2285–2292), in the presence of various protease inhibitors.
In bovine lens maximum activity of FCGAP was found in iris followed by lens cortex and nucleus, retina, sclera, lens epithelium and cornea. The distribution of GST in bovine ocular tissues was somewhat different. The iris had maximum activity followed by cornea and retina. In rat ocular tissues GST activity was maximum in iris followed by retina, lens epithelium and sclera. The lens nucleus had least GST activity. FCGAP activity was maximum in iris followed by cornea and lens epithelium. The time of Ca2+–induced globulization of isolated fiber cells was 22.3±6.2 minutes which doubled in the presence of specific GST inhibitor, Unible–A, and in the presence of Bestatin, globulization was delayed by 2.5 fold.
The results indicate that both the GST and protease activities are present in all the ocular tissues with differential activities and inhibited differentially by GST and protease inhibitors. Use of inhibitors of these enzyme activities may be a novel approach to prevent fiber cell globulization, a process that mimics cataractogenesis.
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