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AN INCREASE OF ORNITHINE δ‐AMINOTRANSFERASE‐MEDIATED PROLINE SYNTHESIS IN RELATION TO HIGH‐TEMPERATURE INJURY IN GRACILARIA TENUISTIPITATA (GIGARTINALES, RHODOPHYTA)
Author(s) -
Lee TseMin,
Chang YuanChun
Publication year - 1999
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1046/j.1529-8817.1999.3510084.x
Subject(s) - proline , biology , ornithine aminotransferase , ornithine , thallus , proline dehydrogenase , biochemistry , nitrate reductase , gracilaria , botany , enzyme , algae , amino acid , arginine
Changes of proline biosynthesis in relation to high‐temperature (35° C) injury were investigated in Gracilaria tenuistipitata var. liui Zhang et Xia. On exposure to 35° C, the specific growth rate decreased after 5 days while free proline levels increased gradually after 2 days and reached the maximal level on days 4–6 but decreased at day 7. The repair ability of thalli treated at 35° C by measuring the growth rate after transfer to 25° C for another 5 days decreased in thalli that had been grown at 35° C for more than 2 days, and the extent increased as treatment at 35° C was prolonged. After 4 days of treatment at 35° C, the activities of both ornithine δ‐aminotransferase (δ‐OAT; EC 2.6.11.3) and Δ 1 ‐pyrroline‐5‐carboxylate reductase (P5CR; EC 1.5.1.2) increased, but that of γ‐glutamyl kinase (γ‐GK; EC 2.7.2.11) remained unchanged, and that of glutamate‐5‐semialdehyde dehydrogenase (GSAd; EC 1.4.1.3) decreased. The application of 10 μM gabaculine, an irreversible inhibitor of δ‐OAT, at 35° C recovered the growth ability but inhibited the increase of both δ‐OAT activity and free proline level; its effects were reversed by 1 mM proline. G. saliconia, which is relatively tolerant to high temperature, showed a decrease of both δ‐OAT activity and free proline level at 35° C. It seems that a stimulation of proline synthesis from the ornithine pathway via an increase in both δ‐OAT and P5CR activities might be associated with high‐temperature injury in G. tenuistipitata.