Human progelatinase A can be activated by autolysis at a rate that is concentration-dependent and enhanced by heparin bound to the C-terminal domain.
Activation of the latent precursor of human gelatinase A (progelatinase A) was investigated using recombinant proenzyme purified from culture medium conditioned by transfected mouse myeloma cells. A 4.0 microM progelatinase A solution was activated to a maximum of 48% of the activity produced by 4-aminophenylmercuric acetate (APMA) simply by its incubation at 37 degrees C for 12 h, though at lower starting concentrations the rate and extent of activation were reduced. Activation was shown to be the result of a single autolytic cleavage at the Asn80-Tyr81 peptide bond that removes the propeptide and converts the M(r) = 72,000 proenzyme into the M(r) = 66,000 active species also produced by APMA activation. It is proposed that this cleavage is a bimolecular event catalysed by previously activated gelatinase A. The addition of heparin increased by approximately eightfold the initial rate of progelatinase A autolytic activation but did not affect the activation of a deletion mutant that lacked the C-terminal domain [des-(418-631)progelatinase A]. The inference that this increase resulted from an interaction between heparin and the C-terminal domain was supported by the finding that, unlike des-(418-631)gelatinase A, both full-length gelatinase A and the isolated C-terminal domain were able to bind to heparin-Sepharose CL-6B and that, at NaCl concentrations sufficient to abolish this binding, heparin had no effect. We conclude that heparin is able to enhance autolytic activation by acting as a template that approximates active-->latent gelatinase A and suggest that a similar mechanism may account for the cell-surface activation of this enzyme.
Crabbe
T
T
Department of Oncology Biology, Celltech Research, Slough, England.
Ioannou
C
C
Docherty
A J
AJ
D000595:Amino Acid Sequence; D001665:Binding Sites; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000302:isolation & purification / Q000378:metabolism*; D018093:Gelatinases / Q000302:isolation & purification / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D020778:Matrix Metalloproteinase 2; D008666:Metalloendopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012965:Sodium Chloride
D004792:Enzyme Precursors; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012965:Sodium Chloride; D006493:Heparin; D018093:Gelatinases; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2