preiss@msu.edu
        Phone: (517) 353-3137
        Home Department: Biochemistry & Molecular Biology,
        Home Page Biochemistry & Molecular Biology

Professor of Biochemistry and Molecular Biology; Ph.D., Duke University, 1957

       Plants and bacteria use similar reactions to synthesize the major carbohydrate reserve polymers, starch and glycogen. First, ADP-glucose (ADPGlc) is synthesized from ATP and glucose-l-P via catalysis by ADPGlc pyrophosphorylase. The glycosyl portion of the sugar nucleotide is then transferred to the non-reducing end of a growing glucose polymer chain to form new 1,4-glucosyl linkages. The synthesis of the a-1,6-glucosidic linkage is catalyzed by branching enzyme. Regulation of starch and glycogen synthesis occurs via allosteric regulation of the ADPGlc pyrophosphorylase-catalyed reaction. Glycolytic intermediates are activators and either AMP, ADP or Pi are inhibitors. In maize and other plants, similar observations have been made in the endosperm. The glycolytic intermediate activators of the ADPGlc pyrophosphorylase vary for many of the systems studied, and a rough correlation has been seen with respect to the nature of the activator and the major carbon assimilation pathway in the organism. For example, the activator for the higher plant ADPG pyrophosphorylases is 3-phosphoglycerate and the major activator for the ADPG pyrophosphorylase of the bacteria that utilize glycolysis as their major catabolic pathway is fructose-1,6-P2. Thus, it is of great interest to determine and compare the structure and function of the catalytic and effector sites of the bacterial and plant ADP glucose pyrophosphorylases. Recombinant DNA techniques are employed to clone the bacterial glycogen and starch biosynthetic enzymes in order to obtain levels so protein purification can be facilitated. Via DNA sequencing, we have deduced the amino acid sequences of the various enzymes. The isolation of several mutants affected in the allosteric function of the E. coli ADPG pyrophosphorylase has been achieved and their genes have been cloned. By DNA sequencing, we have determined the nature and location of the amino acid substitution. This has enabled us to do in vitro mutagenesis to further delineate structure and function of the effector sites. Using modern protein analyses and molecular modeling techniques we are studying the various domains involved in allosteric function and catalysis. Another major effort is to crystallize the ADPGlc pyrophosphorylases and branching enzymes in order to obtain their three-dimensional structure. Transfection of higher plants with the allosteric E. coli mutants has resulted in an increase of starch content in the plants and thus the study of these systems are also important on a commercial basis. We are also studying the bacterial and plant branching enzymes (BE) by the same above techniques to determine their catalytic mechanisms of various plant BE isoymes with respect to their different sizes of branch chains formed and differences in substrate preference of amylose or amylopectin.

Selected Publications

Ballicora, M.A., J.B. Freuauf, Y. Fu, P. Schürmann, and J. Preiss. 2000. Activation of the potato tuber ADP-glucose Pyrophosphorylase by thioredoxin. J. Biol. Chem. 275:1315-1320.

 Binderup, K., L. Watanabe, I. Polikarpov, J. Preiss, and R.K. Arni. 2000. Crystallization and preliminary X-ray Diffraction analysis of the catalytic subunit of ADP-glucose pyrophosphorylase from potato tuber. Acta Crystallographica. D56:192-194.

 Wu, M.-X., and J. Preiss. 1998. The N-terminal region is important for the allosteric activation and inhibition of the Escherichia coli ADP-glucose pyrophosphorylase. Arch. Biochem. Biophys. 358:182-188.