ASPARAGINASE, ALLANTOINASE AND GLUTAMINE-SYNTHETASE ACTIVITIES IN SOYBEAN COTYLEDONS GROWN-INVITRO

Immature soybean cotyledons were cultured in vitro with glutamine, asparagine or allantoin as sole source of N, and the activities of asparaginase, allantoinase and glutamine synthetase measured over eight days. On a cotyledon basis, allantoinase and glutamine synthetase activities increased substantially, independent of the N source. Asparaginase activity also increased markedly in cotyledons grown on asparagine or allantoin. The increases in activity of both asparaginase and allantoinase were not, therefore, specific for growth on their substrates, which suggests that they may be constitutive enzymes. No increase in asparaginase activity occurred in cotyledons grown on glutamine. This effect of glutamine was also observed when included with asparagine. Cotyledons with higher initial asparaginase activity showed a decrease in activity when cultured with glutamine. It is suggested that the negative effect of glutamine on asparaginase may be due to repression. © 1990.