The objective of this project was to obtain a source of diamine oxidase (DAO) necessary for large-scale production of a simple and rapid dipstick method for determining histamine in processed and fresh seafood products. Human diamine oxidase cDNA was inserted into two different vectors designed to secrete the enzyme into the media of cultured insect (Drosophila) cells. Neither expression of cloned DAO from insect cells, nor optimized purification procedures from pig kidneys, have to date provided sufficient quantities of enzyme. The investigators were able to obtain the human diamine oxidase cDNA and subclone it into two expression vectors. However, expression of the diamine oxidase cDNA proved much more difficult than anticipated. The investigators obtained no discernable expression at all in their insect cells. One problem might be the existence of a single nucleotide mutation or deletion somewhere in the clone. The investigators believe that a likely reason for their inability to detect DAO in transiently transfected cells is that the transfection was inefficient and too few cells were producing enzyme. The investigators will continue attempts to express the human DAO in insect cells since they believe this is the best solution to the expression problem.