NUCLEOSIDE CATABOLIZING ACTIVITIES IN SELECTED SEEDS

Abstract

The efficacy of pyrimidine and purine nucleotide metabolism plays a critical role in the progression of biological systems. The process of nucleotide degradation exists in all organisms. The nucleoside degradation and salvage of nucleotides, nucleosides, and nucleobases require several enzymes including deaminases and nucleosidases. Deaminases play a substantial role in the course of removing amino groups from selected nucleobases to convert one nucleoside to another. The cleavage of the N-glycosidic bond in nucleosides is catalyzed by the nucleoside hydrolases or nucleosidases. This process facilitates the recycling of nucleobases.

Nucleoside degradation protein extracts were assessed in some seed sources including Alaska pea, okra, organic okra, peas (Cascadia Sugar Snap), yellow lupin, soybean, spinach, and cantaloupe. Extracts of un-germinated seeds were incubated with reaction mixtures containing 1 mM uridine, inosine, purine riboside, cytidine, adenosine, or 2'-deoxyadenosine in 10 Mm Tris pH 7.2 buffer. Using an HPLC with a Kinetex 5 μ, EVO C18 reverse phase column eluted with ammonium phosphate/ methanol, nucleosidase and deaminase activities were quantified. The results show the existence of active nucleosidases and deaminases in seeds tested. However, there were differences in the levels of activities based on the plant and substrate observed. Uridine, cytidine, and thymine exhibited the highest levels of activity among the nucleosides, while lower activities were observed with guanosine, purine riboside, inosine, and 2'-deoxyadenosine. Among the seeds, soybeans had the lowest activity levels, while okra had the highest activity levels.