CHARACTERIZATION OF ADENOSINE NUCLEOSIDASE FROM ALASKA PEA SEEDS

Abstract

Adenosine nucleosidase was purified from Alaska pea seeds five days after germination. A 4-fold purification has been reached with a 1.3 % recovery. The subunit molecular weight of adenosine nucleosidase was determined by mass spectrometry to be 26,103 daltons. The number of subunits was 1. The Michaelis constant, Km, and the maximum velocity, V max, for adenosine were determined to be 137 48 M, and 0.34 0.02 M/min respectively.

In addition, the substrate specificity of the enzyme was investigated. Based on the observed substrate specificity, adenosine nucleosidase from Alaska pea seeds belongs to the non-specific inosine-uridine nucleoside hydrolases (IU-NHs). An interesting finding was the fact that the purified enzyme was the only plant source that used 2, 3, and 5-deoxyadenosine as substrates. This is completely different from the parasitic protozoa IU-NH, specifically the nucleoside hydrolase from C. fasciculata, which showed no activity toward deoxynucleosides. This difference also indicates that adenosine nucleosidase from Alaska pea goes through a different mechanism of reaction from that of parasitic protozoa. While these results provide insight about the enzyme from Alaska pea seeds, further conformation is required to support the statements above.