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Nitrate uptake in marine phytoplankton: Comparison of half‐saturation constants from seven species 1
Author(s) -
Falkowski Paul G.
Publication year - 1975
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1975.20.3.0412
Subject(s) - phytoplankton , dinoflagellate , enzyme , kinetics , enzyme kinetics , atpase , chemistry , nitrate , michaelis–menten kinetics , biology , saturation (graph theory) , enzyme assay , algae , biochemistry , biophysics , environmental chemistry , botany , ecology , nutrient , active site , physics , mathematics , quantum mechanics , combinatorics
Seven species of marine phytoplankton were assayed for the presence of a NO 3 − ,CI − ‐activated ATPase, thought to be associated with the cell membrane. Only the single dinoflagellate tested, Amphiclinium carterae, failed to show ATPase activity, while the specific activity of the enzyme ranged over one order of magnitude in the other species examined. It is suggested that the enzyme is primarily responsible for the active transport of NO 3 − across the plasmalemma and furthermore the K m for NO 3 − activation of the enzyme is physiologically manifested by K s values for NO 3 − uptake by whole cells. The enzymatic mechanism may explain the observed Michaelis‐Menten kinetics for NO3 − uptake.