title: The binding of zinc to angiotensin-converting enzyme.
abstract: The equilibrium constant for the dissociation of zinc ion from angiotensin-converting enzyme (ACE) was measured using zinc ion buffers of zinc chloride and nitrilotriacetic acid (NTA). The dissociation constant is 6.4 X 10(-10) M. The fraction of active enzyme at equilibrium is independent of the presence of substrate which indicates that hippuryl-histidylleucine binds equally well to the holoenzyme and apoenzyme. The rate constant for the dissociation of zinc from ACE was measured as 0.68 min-1 for the free enzyme; the rate constant for the enzyme substrate complex was roughly 0.18 min-1. The association of zinc ion and ACE is very fast; the rate constant is 1.06 X 10(9) M-1 min-1. Ethylenediaminetetraacetic acid (EDTA) and NTA rapidly remove zinc from ACE with rate constants of 1.27 X 10(3) and 2.2 X 10(3) M-1 min-1. The equilibrium constant for the reaction of NTA with ACE was measured as 4.6 X 10(-2) and was calculated for EDTA as 3.8 X 10(3).
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
authors.forename: J R
authors.initials: JR
authors.lastname: Schullek
authors.forename: I B
authors.initials: IB
authors.lastname: Wilson
mesh_terms: D001665:Binding Sites; D007700:Kinetics; D008433:Mathematics; D009842:Oligopeptides / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; C010980:hippuryl-histidyl-leucine; D007703:Peptidyl-Dipeptidase A; D015032:Zinc