title: Dynamics of nitric oxide rebinding and escape in horseradish peroxidase.
abstract: Ultrafast kinetic measurements of NO rebinding to horseradish peroxidase (HRP) are reported for the first time. The geminate kinetics are found to be exponential for all HRP samples studied. The ferric forms of HRP have NO geminate recombination time constants in the range of 15-30 ps, while the ferrous form has a time constant of approximately 7 ps. The simple exponential NO geminate kinetics found for HRP demonstrate that heme relaxation is not the underlying source of the nonexponential NO rebinding in myoglobin (Mb). The NO ligand escape rates from HRP are also determined, and they are found to depend dramatically on the presence or absence of the competitive inhibitor benzohydroxamic acid (BHA). The kinetic results indicate that, in contrast to Mb, there is direct solvent access to the distal heme pocket of HRP.
authors.affiliation: Department of Physics and Center for Interdisciplinary Research on Complex System, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: Xiong
authors.initials: X
authors.lastname: Ye
authors.forename: Anchi
authors.initials: A
authors.lastname: Yu
authors.forename: Paul M
authors.initials: PM
authors.lastname: Champion
mesh_terms: D001667:Binding, Competitive; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D006877:Hydroxamic Acids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism; D010782:Photolysis
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D006877:Hydroxamic Acids; D009211:Myoglobin; D009569:Nitric Oxide; D006735:Horseradish Peroxidase; C006696:benzohydroxamic acid