Abstract
Isopropylmalate dehydrogenase (IPMDH) is the third enzyme specific to leucine biosynthesis. It catalyzes the oxidative decarboxylation of 3-isopropylmalate (3-IPM) to 2-ketoisocaproic acid. The partially purified enzyme from pea (Pisum sativum L.) shows a broad pH optimum of 7.8 to 9.1 and has Km values for 3-IPM and NAD of 18 and 40 [mu]M, respectively. O-Isobutenyl oxalylhydroxamate (O-IbOHA) has been discovered to be an excellent inhibitor of the pea IPMDH, with an apparent inhibitor constant of 5 nM. As an herbicide, O-IbOHA showed only moderate activity on a variety of broadleaf and grass species. We characterized the herbicidal activity of O-IbOHA on corn (Zea mays L.), a sensitive species; giant foxtail (Setaria faberi) and morning glory (Ipomoea purpurea [L.] Roth), moderately tolerant species; and soybean [Glycine max L. Merr.), a tolerant species. Differences in tolerance among the species were not due to differences in the sensitivity of IPMDH. Studies with [14C]O-IbOHA suggested that uptake and translocation were not major limitations for herbicidal activity, nor were they determinants of tolerance. Moreover, metabolism could not account for the difference in tolerance of corn, foxtail, and morning glory, although it might account for the tolerance of soybean. Herbicidal activity on all four species was correlated with the accumulation of 3-IPM in the plants.
Full Text
The Full Text of this article is available as a PDF (763.8 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Ellerström M., Josefsson L. G., Rask L., Ronne H. Cloning of a cDNA for rape chloroplast 3-isopropylmalate dehydrogenase by genetic complementation in yeast. Plant Mol Biol. 1992 Feb;18(3):557–566. doi: 10.1007/BF00040671. [DOI] [PubMed] [Google Scholar]
- Hurley J. H., Dean A. M., Koshland D. E., Jr, Stroud R. M. Catalytic mechanism of NADP(+)-dependent isocitrate dehydrogenase: implications from the structures of magnesium-isocitrate and NADP+ complexes. Biochemistry. 1991 Sep 3;30(35):8671–8678. doi: 10.1021/bi00099a026. [DOI] [PubMed] [Google Scholar]
- Kohlhaw G. B. Beta-isopropylmalate dehydrogenase from yeast. Methods Enzymol. 1988;166:429–435. doi: 10.1016/s0076-6879(88)66056-3. [DOI] [PubMed] [Google Scholar]
- Ray T. B. Site of action of chlorsulfuron: inhibition of valine and isoleucine biosynthesis in plants. Plant Physiol. 1984 Jul;75(3):827–831. doi: 10.1104/pp.75.3.827. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rhodes D., Hogan A. L., Deal L., Jamieson G. C., Haworth P. Amino Acid Metabolism of Lemna minor L. : II. Responses to Chlorsulfuron. Plant Physiol. 1987 Jul;84(3):775–780. doi: 10.1104/pp.84.3.775. [DOI] [PMC free article] [PubMed] [Google Scholar]