Apricot Seeds as a Source of Dehydrogenases

Increasing interest in various aspects of the mechanism of biological oxidation has developed a need for rich and reliable sources of dehydrogenases. An attempt was made to find such sources in appropriate plant material because of the possibility that such material might have an advantage in cheapness and in ease of handling. With the exception of yeasts, plants do not seem to have been much explored for dehydrogenases. Three samples of yeast from different manufacturers were found to be relatively poor sources for dehydrogenases, and samples from the same source varied greatly in such enzyme activity.

Preliminary search through representative available plant sources indicated the relative richness in dehydrogenases of the coatings of the seeds of various species of Prunus. With the skins removed, the seeds contain almost no dehydrogenases but are rich in lipases and emulsin. Such vegetables as beets and potatoes seem to be poor sources of dehydrogenases. Seeds of legumes and cereals are reported to be good sources of lactic dehydrogenase. 1 Representative assay data on dehydrogenase content are shown in Fig. 1 for extracts from beets, potatoes, yeast and seed coatings of almond, cherry, peach and apricot. Of these materials apricot seed coatings appear to be richest in dehydrogenases.

In extracting the dehydrogenases from fruit seeds, the seeds were first soaked for 24 hours in cold water to each liter of which one-half cc. of toluene was added. The skins were removed and extracted in a ball mill with disodium phosphate containing toluene, for 6 hours. To one liter of phosphate, 100 gm. of wet seed skins were added. The first extract contained most of the lactic and formic dehydrogenases. This was filtered and the skins extracted for another 6 hours with disodium phosphate. This second extract contained most of the malic, tartaric, and oxalic dehydrogenases. It was sometimes possible to separate lactic dehydrogenase from formic dehydrogenase by adsorbing the latter on alumina in acid buffer of pH 6.5. Formic dehydrogenase was then eluted with disodium phosphate. The phosphate filtrates were neutralized with dilute acetic acid and the enzyme precipitated with 5 volumes of 95% ethyl or methyl alcohol. The precipitate was centrifuged, washed with 95% alcohol, then ether, and dried in a vacuum desiccator over calcium chloride. The resulting material is gray and brittle.