The high molecular weight urinary matrix metalloproteinase (MMP) activity is a complex of gelatinase B/MMP-9 and neutrophil gelatinase-associated lipocalin (NGAL). Modulation of MMP-9 activity by NGAL

J Biol Chem. 2001 Oct 5;276(40):37258-65. doi: 10.1074/jbc.M106089200. Epub 2001 Aug 2.


Detection of matrix metalloproteinase (MMP) activities in the urine from patients with a variety of cancers has been closely correlated to disease status. Among these activities, the presence of a group of high molecular weight (HMW) MMPs independently serves as a multivariate predictor of the metastatic phenotype (). The identity of these HMW MMP activities has remained unknown despite their novelty and their potentially important applications in non-invasive cancer diagnosis and/or prognosis. Here, we report the identification of one of these HMW urinary MMPs of approximately 125-kDa as being a complex of gelatinase B (MMP-9) and neutrophil gelatinase-associated lipocalin (NGAL). Multiple biochemical approaches verified this identity. Analysis using substrate gel electrophoresis demonstrated that the 125-kDa urinary MMP activity co-migrates with purified human neutrophil MMP-9 x NGAL complex. The 125-kDa urinary MMP-9 x NGAL complex was recognized by a purified antibody against human NGAL as well as by a monospecific anti-human MMP-9 antibody. Furthermore, these same two antibodies were independently capable of specifically immunoprecipitating the 125-kDa urinary MMP activity in a dose-dependent manner. In addition, the complex of MMP-9 x NGAL could be reconstituted in vitro by mixing MMP-9 and NGAL in gelatinase buffers with pH values in the range of urine and in normal urine as well. Finally, the biochemical consequences of the NGAL and MMP-9 interaction were investigated both in vitro using recombinant human NGAL and MMP-9 and in cell culture by overexpressing NGAL in human breast carcinoma cells. Our data demonstrate that NGAL is capable of protecting MMP-9 from degradation in a dose-dependent manner and thereby preserving MMP-9 enzymatic activity. In summary, this study identifies the 125-kDa urinary gelatinase as being a complex of MMP-9 and NGAL and provides evidence that NGAL modulates MMP-9 activity by protecting it from degradation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute-Phase Proteins*
  • Blotting, Western
  • Carrier Proteins / metabolism*
  • Carrier Proteins / physiology
  • Enzyme Stability
  • Humans
  • Lipocalin-2
  • Lipocalins
  • Matrix Metalloproteinase 9 / metabolism*
  • Matrix Metalloproteinase 9 / urine
  • Molecular Weight
  • Neutrophils / enzymology
  • Oncogene Proteins*
  • Precipitin Tests
  • Protective Agents / metabolism
  • Proto-Oncogene Proteins
  • Tumor Cells, Cultured
  • Urinary Tract / enzymology*


  • Acute-Phase Proteins
  • Carrier Proteins
  • LCN2 protein, human
  • Lipocalin-2
  • Lipocalins
  • Oncogene Proteins
  • Protective Agents
  • Proto-Oncogene Proteins
  • Matrix Metalloproteinase 9