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NADH oxidase activity of soybean plasma membranes oscillates with a temperature compensated period of 24 min
Author(s) -
Morré D. James,
Morré Dorothy M.
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00293.x
Subject(s) - chemistry , biochemistry , enzyme , enzyme assay , oxidoreductase , thiol , ribonuclease , membrane , rna , gene
Summary The enzymatic activity of a hormone‐stimulated and growth‐related protein disulfide‐thiol oxidoreductase (NADH oxidase) with protein disulfide‐thiol interchange activity of etiolated hypocotyls of soybean oscillates with a period of about 24 min or 60 times per 24 h day. The oscillations were temperature compensated such that the period remained constant at about 24 min between 17 and 37°C, a temperature range over which enzymatic activity varied approximately fourfold (Q 10 of 2). The oscillations were observed with intact tissue sections, with isolated plasma membrane vesicles, and with the detergent‐solubilized and partially purified enzyme. The oscillations were observed both with the oxidation of NADH and in the restoration of activity to scrambled ribonuclease used as a measure of the protein disulfide‐thiol interchange activity. The enzymatic activity which is located at the cell surface may represent a biochemical reaction with a potential function as an ultradian oscillator of circadian time keeping.