Sb. Boggio et al., Changes in amino acid composition and nitrogen metabolizing enzymes in ripening fruits of Lycopersicon esculentum Mill, PLANT SCI, 159(1), 2000, pp. 125-133
The free amino acid content of tomato (Lycopersicon esculentum Mill.) fruit
s from cultivars Platense, Vollendung and Cherry were determined during rip
ening. It was found that glutamate markedly increased in red fruits of the
three cultivars under study. At this stage, the cv Cherry had the highest r
elative glutamate molar content (52%) of all the analyzed tomato fruit cult
ivars. Measurements of nitrogen-assimilating enzyme activities of these fru
its showed a decrease in glutamine synthetase (GS, EC 6.3.1.2) during fruit
ripening and a concomitant increase in NADH-glutamate dehydrogenase (GDH,
EC 1.4.1.3) and aspartate aminotransferase (EC 2.6.1.1) activities. Western
blot analysis of protein extracts revealed that while GS was principally p
resent in green fruit extracts, GDH was almost exclusively observed in the
extracts of red fruits. These results suggest a reciprocal pattern of induc
tion between GS and GDH during tomato fruit ripening. (C) 2000 Elsevier Sci
ence Ireland Ltd. All rights reserved.