Aspects on diamine oxidase activity and its determination.

Homogenate of guinea-pig liver and human placenta, tissues known to be rich in diamine oxidase, were incubated with 14C-putrescine and the metabolites formed were determined. In the incubate of guinea-pig liver, the major metabolites were GABA and some unidentified compound(s); delta1-pyrroline and 14CO2 were also obtained. In both the maternal and fetal parts of human placenta, radioactive GABA and the unidentified compound(s) as well as delta1-pyrroline were found. The results indicate that GABA is an important intermediate in putrescine metabolism. Determination of the amount of delta1-pyrroline is thus not well suited as a measure of the diamine oxidase activity in tissues.