Algae. 1999; 14(3): 189-194.

Identification and Characterization of Nitrate Reductase in a Marine Dinoflagellate, Alexandrium tamarense

Kyoung-Jae Choi, Chi-Hun Ha, Myung-Soo Han, Joong-Kyun Jeon, Ki-Tae Kim, Hae-Ok Lee, Moon-Young Yoon

Department of Chemistry and Department of Life Science, Hanyang University. Faculty of Marine Bioscience & Technology, Kangnung Nat. University. Seoulin Research Institute of Life Science, Seoulin Scientific Co., Ltd.

The Nitrate reductase (NR) from the toxic phytoplankton, Alexandrium tamarense, has been identified by the diazo coupling assay method that was based on the formation of a red azo compound. Addition of polyvinylpyrrolidone(PVP) to the extract buffer showed the highest NR activity. The crude extract of A. tamarense has an NR specific activity of 0.0027 U/mg, which is lower than the NR activities found for other algae. The optimum pH for enzymatic reaction was 8.0 and the optimum temperature for maximum activity was 25℃. The apparent Michaelis-Menten constants(K sub(m)) in the diazo coupling nitrate reductase assay are 63 μM for NADH and 14 μM for NO sub(3) super(-), respectively. The NR of A. tamarense was NADH specific, while NADPH also revealed small nitrate-reducing activity like most of the algae.

Keywords : Alexandrium tamarense, Characterization, dinoflagellate, identification, nitrate reductase