Reaction of formate with the fast form of cytochrome oxidase: a model for the fast to slow conversion.
The ability to isolate preparations of cytochrome oxidase which are highly homogeneous has facilitated a study of the effects of various reagents on the purified enzyme. The addition of either sodium formate, formamide, formaldehyde, or sodium nitrite to enzyme which reacts in a single rapid kinetic phase with cyanide causes a blue-shift of 4-6 nm of the net (cytochrome a + cytochrome a3) Soret maximum. Only the derivative prepared by adding sodium formate demonstrates measurable intensity in the g' = 12 region of the low-temperature electron paramagnetic resonance (EPR) spectrum. This g' = 12 resonance is characteristic of cytochrome oxidase which has undergone a modification at the binuclear center and thereby reacts sluggishly with cyanide. As the site of cyanide binding in resting enzyme as been demonstrated to be CuB [Yoshikawa, S., & Caughey, W.S. (1990) J. Biol. Chem. 265, 7945-7958], it is proposed that formate can bind to CuB and the fast to slow transition is rationalized by using this proposal. The g' = 12 signal is also produced upon the addition of sodium formate to mitochondrial preparations, suggesting that the species responsible for this behavior may have possible physiological relevance. Physical properties of the formate derivative and data for other reagents reacted with the fast-reacting enzyme preparation are presented.
Schoonover
J R
JR
Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77251-1892.
Palmer
G
G
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005557:Formaldehyde / Q000378:metabolism; D005559:Formamides / Q000378:metabolism; D005561:Formates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008929:Mitochondria, Heart / Q000201:enzymology*; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism; D013053:Spectrophotometry
D005559:Formamides; D005561:Formates; D009566:Nitrates; C030544:formic acid; D005557:Formaldehyde; C031066:formamide; C031618:sodium nitrate; D003576:Electron Transport Complex IV