Abstract
A possible error in spectrophotometric determination of cinnamate, the product of phenylalanine ammonia-lyase activity, using nonpurified protein extracts has been shown.Under optimal conditions for phenylalanine ammonia-lyase activity, with borate buffer and in the presence of alpha-keto acids, phenylpyruvate is produced and its enol tautomer-borate complex formed, strongly absorbs at 290 nanometers.