Human prochymase activation. A novel role for heparin in zymogen processing.
Human prochymase is packaged with heparin in mast cell granules and appears to be activated by dipeptidylpeptidase I. We show that a high affinity interaction between heparin and prochymase allows the 2-residue propeptide to be cleaved by dipeptidylpeptidase I. A conserved Glu in the propeptide is necessary for this heparin effect. Following propeptide cleavage, capture of the newly generated NH2 terminus by an "activation groove" on the enzyme activates the enzyme and concurrently prevents a progressive degradation of the NH2 terminus by dipeptidylpeptidase I. Surrogate peptide studies show that the activation groove is unoccupied in prochymase and is specific for the chymase NH2 terminus. These observations indicate that heparin is an important cofactor in the prochymase activation process and explain how dipeptidylpeptidase I, a nonspecific processing enzyme, can effect a specific cleavage of the zymogen propeptide.
Murakami
M
M
Department of Molecular Cardiology, Cleveland Clinic Foundation, Ohio 44195.
Karnik
S S
SS
Husain
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D053818:Chymases; D017931:DNA Primers / Q000737:chemistry; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012697:Serine Endopeptidases / Q000378:metabolism*; D013329:Structure-Activity Relationship
D017931:DNA Primers; D004792:Enzyme Precursors; D006493:Heparin; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D012697:Serine Endopeptidases; D053818:Chymases