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United States Department of Agriculture

Agricultural Research Service

Title: Non Peroxidase Oxidation of Guaiacol

Authors
item Vierling, R - IN CROP IMPROVEMENT ASSOC
item Palmer, Reid
item Wilcox, James

Submitted to: Seed Technology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1997
Publication Date: N/A

Interpretive Summary: An identifying trait for soybean varieties is the presence of either high or low activity of peroxidase, an enzyme in soybean seed coats. High or low peroxidase activity has been determined using a chemical test known as the guaiacol test. Soybean with high peroxidase has about 68 times the peroxidase activity as soybean with low peroxidase. Recently, an antibody test for peroxidase has been developed as an alternative to the guaiacol test. Comparative tests of the two methods of detecting peroxidase activity in seeds of stored soybean samples indicated the antibody test was more accurate than the guaiacol test. The guaiacol test apparently was reacting with enzymes in the seed coats other than the peroxidase enzyme, resulting in false high peroxidase activity readings. Use of the antibody method of testing for peroxidase activity will result in more accurate determinations of seed purity in stored soybean samples than will the guaiacol test. This will be helpful to certification agencies that are responsible for identifying soybean varieties and for determining genetic purity of these varieties.

Technical Abstract: The peroxidase test for soybean [Glycine max (L.)] Merrill] is a standard assay used in the identification of soybean cultivars. Cultivars are divided into two groups based on the presence of either high or low seed coat peroxidase activity. High or low activity is based on the observed color change associated with oxidized guaiacol. Seed coat peroxidase activity also can be measured using the soybean peroxidase capture assay (SPCA), which used a monoclonal antibody to isolate the enzyme from biological samples. Unlike the SPCA, the guaiacol assay does not separate the peroxidase enzyme from other enzymes or reactive oxygen species. Results showed that 7% of the stored soybean seeds tested, which showed high peroxidase activity using the guaiacol test, showed no measurable peroxidase activity using SPCA. This suggests that the initial guaiacol oxidation resulted from non enzymatic oxidation of guaiacol by reactive oxygen species or other oxidative enzymes and not from seed coat peroxidase enzymatic activity.

Last Modified: 12/18/2014
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