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KMID : 0380219990320040393
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Journal of Biochemistry and Molecular Biology
1999 Volume.32 No. 4 p.393 ~ p.398
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Separation and Characterization of Two Forms of Acetolactate Synthase from Etiolated Pea Seedlings
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Shin Yong-Soo
Chong Chom-Kyu
Choi Jung-Do
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Abstract
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Acetolactate synthase (ALS) catalyzes the first reaction common to the biosynthesis of L-valine, L-leucine, and L-isoleucine. ALS is the target site of several classes of herbicides, including the sulfonylureas, the imidazolinones, and the triazolopyrimidines. Two forms of ALS (ALS I and ALS II) which have different affinity for Heparin have been separated from etiolated pea seedlings. The substrate saturation curves of both ALS I and ALS II were hyperbolic in contrast to previous reports. The two forms of ALS showed significant differences in their physical and kinetic properties. The values of Km for ALS I and ALS II were 9.0 mM and 4.8 mM, respectively. The pI values for ALS I and ALS II were determined to be 5.3 and 5.75 by isoelectric focusing, respectively. The native molecular weights for ALS I and ALS II obtained by nondenaturing gel electrophoresis and activity staining were 124 and 244 kDa, respectively. They also exhibited different sensitivity to feedback inhibition by end-product amino acids and inhibition by Cadre, an imidazolinone herbicide.
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KEYWORD
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Acetolactate synthase, Herbicide, Pea
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