SURVEY OF NUCLEOSIDE DEGRADING ENZYME ACTIVITIES IN SOYBEAN, CORN AND YELLOW LUPIN

Abstract

Efficient pyrimidine and purine nucleotide metabolism is essential for healthy growth and development of all organisms. Significant energy cost reduction and a mutation bypass mechanism is afforded via the recycling pathways of nucleotide metabolism in microorganisms, animals and plants. Numerous enzymes are involved in the degradation and salvage of nucleotides, nucleosides and nucleobases. Nucleosidases, phosphorylases and deaminases contribute during the degradation of deoxyribonucleotides and ribonucleotides.

Presence of nucleosidase, phosphorylase and deaminase activities were evaluated in 5- 7 day old yellow lupin seedlings and 5-9 day old soybean seedlings. Nucleosidase and deaminase activities were also assessed in 5-7 day old corn seedlings. Nucleosidases catalyze hydrolytic cleavage of the ribose moiety of the nucleoside and were found active in all three plants species surveyed. Significant variation was noted in the level of activity observed between yellow lupin and soybean, both legumes. Phosphorylases mediate a reversible reaction that breaks the ribose away from the nucleobase in the presence of phosphate ions and may be present in yellow lupin. Adenosine phosphorylase is likely active in soybean. Deaminases assist in the interconversion of nucleosides. Cytidine deaminase activity was found in all three plants. Adenosine/adenine deaminase activity was observed in soybean and corn but not in yellow lupin. Nine nucleosides were evaluated as substrates and specific activities are reported.