Photochemical cis-trans isomerization of furylacryloylpeptides and their different kinetic behavior as substrates for carboxypeptidase Y.

Furylacryloyl substrates used in kinetic measurements of proteolytic enzymes are shown to cis-trans photoisomerize quickly in plain daylight. The enzymatic transformation of the two forms is sufficiently different to cause problems for such measurements without careful protection against light.