摘要:

Neutral proteolytic activity, having a pH optimum of about 7, was present in the high molecular weight fraction of bovine interphotoreceptor matrix (IPM) separated by gel filtration on Sephacryl S-500. The enzyme(s) was active toward a number of exogenous substrates, including albumin, Azocoll, and gelatin. However, it was inactive toward a synthetic substrate for bacterial collagenase. Proteolytic activity was proportional to protein; however, the time course of the reaction was nonlinear, suggesting that“activation”of a precursor form might be necessary. Of a number of specific inhibitors tested, those directed toward metalloproteinases (1,10-phenanthrqline>EDTA>EGTA) proved most effective. While activity was also inhibited by sulfhydryl reagents and dithiothreitol, inhibitors specific for cysteine protein-ases were ineffective. Higher specific activity was present in IPM obtained from retinal pigment epithelium (RPE) than from retina.An endogenous proteinase inhibitor(s) was also found in IPM from both RPE and retina. It was effective against the endogenous metalloproteolytic activity of IPM and also against thermolysin, but not against trypsin or papain. Fractionation of IPM on Sephacryl S-500 revealed a broad peak of inhibitory activity at molecular weights of less than 105daitons.This is the first report of the presence of neutral proteolytic activity and metalloproteinase inhibitor(s) in bovine IPM. These materials may function in concert to maintain the proper level of various components within this matrix.

ISSN:0271-3683    

DOI:10.3109/02713689209069171

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The 115kDa cytoskeletal beaded filament protein of bovine lens fibres is degraded during opacification induced by increased internal calcium. The monoclonal antibody R2D2 to this protein has been used in whole lenses and native homogenates to follow the process of degradation and the production of break-down products. In the opaque outer cortex of whole bovine lenses with an internal Ca2+of 2.0mM, both the 115kDa parent protein and the main degradation product (57kDa) were reduced in amount by almost 60%. No additional products were detected by the antibody. When native homogenates were incubated overnight with 10mM Ca2+the protein could no longer be detected in SDS gels, but faintly reactive bands were detected by the antibody. Since these changes were dependent on the presence of increased calcium they were compared with changes induced by incubating freshly isolated cytoskeletal proteins with Ca2+and the Ca2+-activated protease, calpain. The 115kDa protein was shown to be susceptible to degradation by calpain, with the formation of a number of breakdown products. These results indicate that degradation of the beaded filament protein can be brought about by the activation of calpain. Since the enzyme is present in lens cortex it is likely to have a role in the protein degradation observed during Ca2+-induced opacification, and may also be involved in the changes occurring as the lens fibres mature.

ISSN:0271-3683    

DOI:10.3109/02713689209069172

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Cataract: Biochemistry Epidemiology and Pharmacology, edited by J. Harding, published by Chapman and Hall, New York, 1991.

ISSN:0271-3683    

DOI:10.3109/02713689209069173

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor