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http://hdl.handle.net/1834/965
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| Title: | Some Properties of Glutamate Dehydrogenase from the Marine Red Alga Gracilaria sordida (Harv.) W. Nelson |
| Authors: | Mtolera, M.S.P. |
| ASFA Terms: | Algae |
| Issue Date: | 2003 |
| Publisher: | WIOMSA |
| Citation: | Western Indian Ocean J. Mar. Sci., 2 (2), p. 179–186 |
| Abstract: | Glutamate dehydrogenases (GDH, EC 1.4.1.2-4) catalyse the entry of ammonium
into the organic cycle via amination of a-ketoglutarate and its release via deamination of Lglutamate.
NAD-GDH facilitates NAD-/NADP-dependent deamination while NADPH-GDH
facilitates NADH-/NADPH-dependent amination reactions. In the study reported here, GDHs
were extracted from the red alga Gracilaria sordida and purified 10- to 180-fold before
examining their amination and deamination reaction properties. NAD-/NADP- and NADH-/
NADPH-dependent activities were the order of 11:1 and 1:1.8, respectively. The pH optima for
amination and deamination were 8.2 and 8.4 under NADH- and NADPH- and 8.4 and 9 under
NAD- and NADP- dependent activities, respectively. Whereas both NAD- and NADP-dependent
deamination activities were activated by calcium ions (Ca2+), only NADPH-dependent amination
was activated. The Km values (in mM) were 3.0–3.6 for ammonia, 2.0–3.3 for a-ketoglutarate,
0.00286 for NADH, 0.0033 for NADPH),1.7–2.1 for L-glutamate, 0.344 for NAD and 0.476
for NADP. It appears that the GDHs in G. sordida are dominated by NAD-dependent deamination
enzyme and that in NADH-NADPH- dependent amination reactions, NADPH is more preferred.
It is suggested that NAD-GDH’s role in G. sordida could be as a catabolic shunt facilitating
respiration. Anabolic functions could be assimilation of ammonia released during
photorespiration and synthesis of N-rich transport compounds. |
| URI: | http://hdl.handle.net/1834/965 |
| ISSN: | 0856-860X |
| Appears in Collections: | Miscellaneous
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