Comparison of techniques for measurement of gelatinases/type IV collagenases: enzyme-linked immunoassays versus substrate degradation assays

Radiolabeled substrate degradation assays and gelatin zymography are routinely employed to assay 72 kDa gelatinase A (MMP-2) and 92 kDa gelatinase B (MMP-9) in biological fluids. Enzyme-linked immunosorbent assays (ELISA) have recently been developed for the quantitation of these matrix metalloproteinases (MMP). In this study, we have compared ELISA to standard substrate degradation assays for measurement of MMP-2 and MMP-9 in human plasma and tumor-conditioned media. Gelatin Sepharose chromatography and gel filtration chromatography were employed as partial purification procedures for MMP-2 and MMP-9. The ELISA data for MMP-2 and MMP-9 are linear on a log:log regression curve over a wide range of MMP concentrations and are specific for the designated gelatinase, with no overlap detected with related metalloproteinases. The minimum detectable concentrations of MMP-2 and MMP-9 were approximately 0.5 ng/ml and 0.2 ng/ml, respectively, in the ELISA as compared to 4 ng/ml and 3 ng/ml, respectively, in gelatin zymography. The [3H]gelatin degradation assay required a combination of >50 ng/ml of MMP-2 and MMP-9 for detection. Although gelatin zymography was less sensitive than ELISA (primarily due to the smaller sample volume employed) and was more difficult to quantitate, this procedure offers the important advantage of being able to distinguish between latent and activated gelatinases.