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Determination of the Apparent K m of Nitrate Reductase from Spinach Leaves for NADH by a Coupled Assay
Author(s) -
Sanchez J.,
Heldt H. W.
Publication year - 1989
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1989.tb00092.x
Subject(s) - spinach , nad+ kinase , nitrate reductase , nitrate , chemistry , reductase , enzyme , cytosol , biochemistry , chromatography , organic chemistry
Using a novel coupled enzyme activity assay, with a partially purified preparation of spinach leaf nitrate reductase, the apparent K m for NADH was determined as 1.4 μM. These measurements were carried out in the presence of 0.5 mM NAD, which is within the physiological range found in the cytosol of a leaf cell. The results show that an NADH/NAD ratio of 3 × 10 −3 is sufficient for a half maximal rate of nitrate reductase.