Interaction of the hemin 2 and 4 substituents with apo horseradish peroxidase

2-formyl, 4-vinyl deuterohemin (1) and 2-vinyl, 4-formyl deuterohemin (2) substituted horseradish peroxidases have been prepared from apoperoxidase and the respective hemins. The two hemins bind at different rates to the apoprotein and the resultant substituted peroxidases possess different visible spectra and activities. These results indicate that the hemin 2 and 4 substituents interact with apoperoxidase and are not exposed to the solvent.