Purine salvage in cotyledons of germinating lupin seeds

Abstract

Purine metabolism is much less elucidated in plants [ 1,2] than in animal tissues. In contrast to animal tissues, in plants adenosine is hydrolyzed to adenine and ribose by adenosine nucleosidase (EC 3.2.2.7.) found in leaves of various species [3-71, as well as in the cotyledons of yellow lupin seedlings [8]. For the cotyledons, the highest adenosine nucleosidase activity has been observed on day 4-5 of seed germination [9]. However, as Brown found [ IO,1 l] in legume seeds, adenine does not accumulate in their cotyledons at any stage of germination. This could suggest that the activity of purine salvage pathways is relatively high. The aim of this work was to study changes in the activity of enzymes of the purine salvage pathways in cotyledons of germinating lupin seeds. In animals, two ways of purine salvage are postulated: (i) The one-step way catalyzed by purine phosphoribosyltransferases (EC 2.4.2.7. and EC 2.4.2.8.); (ii) The two-step way dependent on purine nucleoside phosphorylase (EC 2.4.2.1.) and nucleoside kinases (EC 2.7.1.20 and 2.7.1.73.) or nucleoside phosphotransferase (EC 2.7.1.77). Some of these enzymic activities have been studied in germinating wheat embryos, but only up to the second day of germination [ 121.