Enzyme-like effect of metmyoglobin on the thermal cis-trans isomerization of stilbazolium betaine.

A photochromic compound, stilbazolium betaine M, when associated with metmyoglobin undergoes an accelerated thermal cis-trans isomerization. A study of the pH and ionic strength dependence of the isomerization reaction rate of the photochrome associated with metmyoglobin was performed. A comparative investigation of the reaction carried out in the presence of three proteins, metmyoglobin, apomyoglobin, and human albumin, indicates a specific influence of the heme pocket environment on the reaction. Possible mechanisms of the reaction acceleration are considered.