Rapid methods for determining decarboxylase activity: ornithine and lysine decarboxylases

A rapid biochemical method for the determination of ornithine and lysine decarboxylase (EC 4.1.1.18) activity has been developed for use in the routine clinical laboratory. It is based on the detection of the amine end product produced in response to the single key amino acid added to a synthetic medium. A modified ninhydrin reagent is used to detect the amine after a chloroform extraction. This procedure can be used with a 1- to 4-hr incubation period (utilizing an initial concentrated inoculum) or with an overnight culture. Thus, measurements based on the alkalinization of the medium after a lengthy incubation period are avoided. Optimal parameters for enzyme activity are discussed.