Amine oxidases in dental pulp : a study with special regard to a semicarbazide-sensitive amine oxidase with catalytic potency towards serotonin

摘要

The amine oxidizing capacity of piglet dental pulp tissue has been investigated. At least six separate enzyme activities could be distinguished: - a soluble semicarbazide-sensitive (SSAO) activity towards benzylamine, most likely to be derived from the content of blood plasma within the pulp tissue; - a soluble pulp tissue SSAO activity with most properties in common with the plasma enzyme, however with great efficiency not only regarding benzylamine but also tryptamine; - a tissue bound SSAO activity with activity towards benzylamine, tryptamine, tyramine and ß-phenylethylamine; - a tissue bound semicarbazide-sensitive activity towards serotonin (SSA0-5HT) (a combination of properties never reported before); - a mitochondrially bound and clorgyline-sensitive monoamine oxidase-A (MAO-A) activity with activity towards serotonin; - a mitochondrially bound and deprenyl-sensitive MAO-B activity with activity towards e.g. benzylamine, tryptamine, tyramine and ß-phenylethylamine. The relative importance of the various activities for the metabolism of some monoamines has been investigated. Although the SSAO enzymes had lower K values with most substrates than the MAO, the bulk of ïhe compounds was likely to be metabolized by MAO-B because of higher V values. K values and values with serotonin, howSver, were rather similar for rfle MAO and the SSAO membrane-bound enzyme(s). The thermal sensitivity of membrane-bound SSAO activities was found to be considerably lower than that for MAO-B. The SSAO-5HT activity was found to be localized to the plasma membrane with a greater activity towards the perifery of the pulp tissue than towards the centre. No great difference in the various amine oxidase activities was found when pulp tissues of varying degrees of maturity were compared. The occurrence of membrane-bound SSAO and MAO activities was investigated and compared between pig, ox and human dental pulp. All activities were found to be present in about the same order of magnitude in all three species with the exception of a higher MAO-A activity in the ox pulp and the absence of this enzyme activity in the human dental pulp.