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Previously, we discovered a new MMP-2 isoform GA110, of which appearance in human follicular fluid(FF) and serum was increased by EDTA. The present study was conducted to investigate how GAI 10 can appear by EDTA. To examine possible involvement of protein disulfide isomerase(PDI), an enzyme responsible for the dimerization of protein via disulfide formation, effect of PDI inhibitor on the appearance of GA110 by EDTA was investigated. When PDI inhibitor added to FF before EDTA treatment, the gelatinolytic activity of GA110 was abolished in a concentration dependent manner. By contrast, the activity of 72 kDa gelatinase increased. However, the PDI inhibitor added to FF after EDTA treatment, the gelatinolytic activity of GA110 was unaffected. To find out the nature of the enzyme which converts 72 kDa gelatinase into GAI 10, chromatographic separation method of FF proteins was done. Using hydroxyapatite column, fractions rich in 72 kDa gelatinase were isolated and pooled. By using this pool as substrate for the 72 kDa converting enzyme, protein fractions containing the converting activity were obtained from chromatographic separation of FF onto glutathione sepharose fast flow column. When immunoblotting was performed on this enzymatically active protein fractions against polyclonal anti-PDI antibody, distinct immunoreactivity was observed, although appeared in smaller molecular weight region. Based on these observations, it is suggested that the appearance of GAI 10 in FF by EDTA treatment could be due to an activation of PDI-like enzyme, which dimerizes 72 kDa gelatinase into GAI 10 via the formation of disulfide bond between molecules.
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