Bieth_1973_Biochemistry_12_3023

Three photochromic reagents were synthesized and examined for their ability to inactivate acetylcholinesterase. They are: N-p-phenylazophenyl-N-phenylcarbamyl chloride (PAPCl), N-p-phenylazophenyl-N-phenylcarbamyl fluoride (PAPF), and N-p-phenylazophenyl-V-methylcarbamyl chloride (PAMCC1). These photochromic compounds can exist as cis and trans isomers that are interconvertible under the influence of light of selected wavelengths. In the trans configuration, the azobenzene portion of the molecule is planar; this is not so for the cis isomers. As a result, the two isomeric forms of each of the reagents acylated the enzyme acetylcholinesterase at different rates; deacylation rates also differed. In all cases, the cis isomers acylated the enzyme at faster rates than the trans isomers. The reverse was true for the deacylation reaction. The most active reagent was PAMCC1. Kinetic constants were evaluated and some observations were made on the utility of photochromic reagents as probes of the topography of biological systems having the property of specificity