EFFECT OF ZINC CONCENTRATION ON THE GELATINOLYTIC ACTIVITY OF TYPE-IVCOLLAGENASES

Despite the ubiquitous nature of zinc metalloenzymes and their necessi ty for all living species, the role of these enzymes in the clinical m anifestations of zinc deficiency or intoxication is not known. Type IV collagenases are zinc metalloproteases which are involved in the path ological and physiological turnover of intercellular matrix. We partia lly purified the 92 kDa and 72 kDa collagenases from serum-free rat gl omerular mesangial cell media. The gelatinase activity was assessed by gelatin-substrate zymography and a recently developed nonradioactive assay. By zymography, increasing concentrations of zinc above 50 muM p rogressively inhibited both enzymes with the greatest effect seen in t he mM range. By the quantitative assay, the 92 kDa activity was fairly constant up to a concentration of 10 muM and complete inhibition was observed above 500 muM. The 72 kDa gelatinase activity, however, reach ed a peak around a zinc concentration of 100 muM and complete inhibiti on was observed above 5000 muM. In the physiological range of tissue a nd serum zinc levels, the activity of both metalloproteinases appears to be very sensitive to changes in zinc concentration. Although the ef fect of this altered gelatinase activity in vivo is not known yet, the turnover of the intercellular matrix is likely to be affected.