Ronald G. Duggleby

University of Queensland

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Luke W. Guddat

University of Queensland

Siew Siew Pang

Monash University

Peter F. Nixon

University of Leeds

Jennifer A. McCourt

Scientific Services

Michael E. McManus

University of California, San Francisco

David T. Dennis

Performance Plants (Canada)

Alan K. Chang

Wenzhou University

Yu‐Ting Lee

National Taipei University of Nursing and Health Science

Judith M. Candy

Lincoln University

Jennifer L. Martin

Griffith University

Cooperative Institutions

University of Queensland

Weatherford College

National Institutes of Health

Centre National de la Recherche Scientifique

Harvard University

University of Wisconsin–Madison

Cornell University

University of Michigan–Ann Arbor

University of California, Los Angeles

Howard Hughes Medical Institute

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Elucidating the Specificity of Binding of Sulfonylurea Herbicides to Acetohydroxyacid Synthase

Biochemistry (2005)

Jennifer A. McCourt Siew Siew Pang Luke W. Guddat Ronald G. Duggleby

Acetohydroxyacid synthase (AHAS, EC 2.2.1.6) is the target for the sulfonylurea herbicides, which act as potent inhibitors of the enzyme. Chlorsulfuron (marketed as Glean) and sulfometuron methyl (marketed as Oust) are two commercially important members of this family of herbicides. Here we report crystal structures of yeast AHAS in complex with chlorsulfuron (at a resolution of 2.19 Å), sulfometuron methyl (2.34 Å), and two other sulfonylureas, metsulfuron methyl (2.29 Å) and tribenuron methyl (2.58 Å). The structures observed suggest why these inhibitors have different potencies and provide clues about the differential effects of mutations in the active site tunnel on various inhibitors. In all of the structures, the thiamin diphosphate cofactor is fragmented, possibly as the result of inhibitor binding. In addition to thiamin diphosphate, AHAS requires FAD for activity. Recently, it has been reported that reduction of FAD can occur as a minor side reaction due to reaction with the carbanion/enamine of the hydroxyethyl−ThDP intermediate that is formed midway through the catalytic cycle. Here we report that the isoalloxazine ring has a bent conformation that would account for its ability to accept electrons from the hydroxyethyl intermediate. Most sequence and mutation data suggest that yeast AHAS is a high-quality model for the plant enzyme.

Sulfonylurea

Acetolactate synthase

10.1021/bi047980a

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Citations (119)

Pyruvate Kinase, a Possible Regulatory Enzyme in Higher Plants

PLANT PHYSIOLOGY (1973)

Ronald G. Duggleby David T. Dennis

A number of plant species were examined for the presence of pyruvate kinase (pyruvate-ATP phosphotransferase, EC 2.7.1.40), and of a phosphatase activity which hydrolyzes phosphoenolpyruvate. Of those examined, only cotton (Gossypium sp. L.) seeds were found to be sufficiently free of the phosphatase to permit a kinetic study of pyruvate kinase.During germination of cotton seeds, pyruvate kinase activity rises for the first 3 days, after which it falls back to its original level. This developmental pattern is characteristic of enzymes involved in the conversion of fat into carbohydrate in fatstoring seeds. The phosphatase also rose rapidly during germination, which precluded the use of extracts from seedlings in the study of pyruvate kinase. No evidence was found for the presence of more than one pyruvate kinase in cotton seedlings.In crude extracts from ungerminated seeds, the enzyme shows slight deviations from normal kinetics with respect to phosphoenolpyruvate, magnesium, and to a lesser extent, ADP. After partial purification of the enzyme by ion exchange chromatography, the enzyme shows normal kinetics. The enzyme is activated by AMP, and inhibited by both ATP and citrate, in both crude and partially purified preparations. It is suggested that cotton seed pyruvate kinase is a regulatory enzyme.

PKM2

10.1104/pp.52.4.312

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Citations (52)

A nonlinear regression program for small computers

Analytical Biochemistry (1981)

Ronald G. Duggleby

Listing (finance)

Computer program

10.1016/0003-2697(81)90104-4

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Citations (563)

Regression analysis of nonlinear Arrhenius plots: An empirical model and a computer program

Computers in Biology and Medicine (1984)

Ronald G. Duggleby

Hyperbola

Arrhenius plot

Computer program

Line (geometry)

Curve fitting

10.1016/0010-4825(84)90045-3

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Citations (313)

The Importance of Conserved Residues in Human Liver UDPglucose Pyrophosphorylase

European Journal of Biochemistry (1996)

Hwan‐You Chang Hwei‐Ling Peng Yu Chao Ronald G. Duggleby

Comparison of the amino acid sequences of five eukaryotic UDPglucose pyrophosphorylases has identified a number of conserved residues that may be important for substrate binding or catalysis. Using the cloned cDNA for the human liver enzyme, we have investigated the role of several of these residues by site‐directed mutagenesis. Changing the single conserved cysteine (residue 123) to serine resulted in an active enzyme, as did mutating the single conserved histidine (residue 266) to arginine. The two conserved tryptophans were each altered to serine; W218S is active while W333S is not. In the latter case, the enzyme does not appear to fold correctly, and a similar result was obtained by mutation to lysine at one (residue 391) of the four conserved arginines. The other three arginines are not essential, as judged by the observation that R389H, R422Q and R445H are all active. The kinetic properties of each active mutant were investigated and in most cases were found to be similar to those of wild‐type. The most dramatic change is a sevenfold increase in the K m for magnesium pyrophosphate with C123S. Overall, none of these conserved residues appears to be essential for activity, although such a role cannot be ruled out for W333 and R391 where mutation resulted in defective folding.

10.1111/j.1432-1033.1996.t01-1-00723.x

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Citations (20)

Non‐Michaelian monooxygenase kinetics: studies using competitive inhibitors

FEBS Letters (1980)

P.E.B. Reilly Daniel J. O’Shannessy Ronald G. Duggleby

10.1016/0014-5793(80)80998-7

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Citations (8)

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Journal of Biological Chemistry (2005)

Akazawa Chihiro Ve Albane Aminova Leila Antonietta Vanoni Mehdi Arbabi‐Ghahroudi

10.1016/s0021-9258(20)58996-5

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Synthesis, crystal structure and herbicidal activity of mimics of intermediates of the KARI reaction

Pest Management Science (2004)

Baolei Wang Ronald G. Duggleby Zhengming Li Jian‐Guo Wang Yonghong Li

Two mimics of the intermediate in the reaction catalyzed by ketol-acid reductoisomerase (KARI) were synthesized. Their structures were established on the basis of elemental analyses, IR, 1H NMR and GC/mass detector. The crystal structure of compound 2 was found to be a substituted dioxane, formed by the condensation of two molecules. The two compounds showed some herbicidal activity on the basis of tests using rape root and barnyard grass growth inhibition. However, the herbicidal effect was weaker in greenhouse tests.

Chemical structure

Molecular mass

Proton NMR

Condensation reaction

10.1002/ps.972

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Citations (54)

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Journal of Biological Chemistry (1974)

Vincent G. Allfrey G.D. Aurbach Ze Barak Jeffrey M. Becker Bhalla Vinod

10.1016/s0021-9258(19)43083-4

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