INTERACTION OF PEPTIDE-SUBSTRATES OF FIBROBLAST COLLAGENASE WITH BIVALENT-CATIONS - CA2+ BINDING BY SUBSTRATE AS A SUGGESTED RECOGNITION SIGNAL FOR COLLAGENASE ACTION

To correlate structural data on substrates of human fibroblast collage nase with their interaction with the enzyme, we have studied: Ac-PLG-s -LLG-O-ethyl ester (I), Dnp-PLGLWA(d-Arg)-NH2 (II), AcGPEGLRVG-O-ethyl ester (III) and Succ-GPLGP-O-amidomethylcoumaryl ester (IV). Peptides I and II represent collagenase cleavage sequences in collagen, peptid e III is a mimic for the cleavage site in alpha(2)-macroglobulin and p eptide IV represents a non-substrate model. Kinetic data showed that p eptides I, II and III were substrates of the enzyme. In contrast, pept ide IV was not acted upon by the enzyme. Circular dichroism data on th e peptides showed that the peptides assume ordered structures in water and trifluoroethanol. In the latter solvent, peptides I and III bound Ca2+ and Zn2+ while peptide II bound Ca2+ but not Zn2+. Peptide IV di d not bind either cation in this solvent. Together with the kinetic da ta, the results suggest that the collagenase cleavage segments in coll agen and non-collagen substrates of collagenase could interact with Ca 2+ and the enzyme to form a ternary complex. This, in turn, would impl y a cofactor role for Ca2+ in collagenase action in addition to the so lely structural role ascribed so far to this cation. (C) 1995 Academic Press, Inc.