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Hydrogen peroxide production by roots and its stimulation by exogenous NADH
Author(s) -
Frahry Gitta,
Schopfer Peter
Publication year - 1998
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1998.1030313.x
Subject(s) - peroxidase , nad+ kinase , chemistry , hydrogen peroxide , catalase , superoxide dismutase , horseradish peroxidase , biochemistry , apoplast , glycine , superoxide , enzyme , cell wall , amino acid
H 2 O 2 production by roots of young seedlings was monitored using a non‐destructive in vivo assay at pH 5.0. A particularly high rate of H 2 O 2 production was measured in the roots of soybean ( Glycine max L. cv. Labrador) seedlings which were used for further investigation of the physiological and enzymological properties of apoplastic H 2 O 2 production. In the soybean root H 2 O 2 production can be stimulated 10‐fold by exogenous NADH or NADPH. This response displays typical features of a peroxidase‐catalyzed oxidase reaction using NAD(P)H as electron donor for the reduction of O 2 to H 2 O 2 . Comparative measurements showed that the NADH‐induced H 2 O 2 production of the roots resembles the H 2 O 2 ‐forming activity of horseradish peroxidase with respect to NADH and O 2 concentration requirements and sensitivity to inhibition by KCN, NaN 3 , superoxide dismutase and catalase. NADH‐induced H 2 O 2 production can be observed with similar intensity in all regions of the root, in agreement with the distribution of apoplastic peroxidase activity. In contrast, the activity responsible for the basal H 2 O 2 production in the absence of exogenous NADH was mainly confined to a short subapical zone of the root and differs from the NADH‐induced reaction by insensitivity to inhibition by superoxide dismutase and a strikingly lower requirement for O 2 . It is concluded that the basal H 2 O 2 production of the root is mediated by an enzyme different from peroxidase, possibly a plasma membrane O 2 − ‐producing oxidase.