Robert P. Metzger

Professor, Biochemistry

office: CSL 312B
phone: 619-594-2710
Metzger photo

Research Interests

My research interests presently cover four major areas:

Enzymes of carbohydrate metabolism: The well-known major pathways of carbohydrate metabolism employ phosphorylated substrates such as glucose-6-phosphate. I am interested in determining the metabolic roles for enzymes that catalyze the oxidation of non-phosphorylated hexoses and pentoses. Some are already known, e.g. aldose reductase and L-iditol dehydrogenase in seminal vesicles combine to convert D-glucose to the D-fructose found in semen. Glucose (hexose-6-phosphate) dehydrogenase, an enzyme of the microsomal fractions of vertebrate livers, may be functional within these membrane systems.The physiological function of another enzyme, L-fucose (D-arabinose) dehydrogenase is unclear. My plans for research on these enzymes include: 1. investigation of in situ microsomal glucose utilization using 14C-hexose substrates; 2. purifying enzymes involved in the observed glucose oxidation for study of their physical properties and primary structures; 3. doing a comparative study of these enzyme activities in animals at various stages of the phylogenic tree.

Diabetes mellitus: This disease is one of the leading causes of blindness, atherosclerosis, and kidney failure; these and other pathological conditions are called “complications of diabetes.” Organs from diabetic animals possess certain enzyme activities, including acid hydrolase activities, in levels that are significantly different from nondiabetic (normal) controls; these changes also occur in human subjects. I am interested in finding out if abnormal levels of certain acid hydrolases are directly connected with the development of diabetic complications. My plans for continued research in this area include: 1. study of the effect of diabetes on additional acid hydrolases, with experimental determination of whether any changes from normal values in diabetic subjects are caused by lack of enzyme synthesis or by inhibition of a given acid hydrolase; 2. test diabetic and normal tissue for concentrations of substances known to be substrates of enzymes whose level of activity is abnormal in organs from diabetic subjects.

Protein-browning (Maillard) reactions: Once only food chemists were interested in studying protein-browning reactions, but now we realize that these reactions also occur under physiological conditions. Browning begins with the nonenzymatic reaction of monosaccharides with protein primary amine groups; this is the basis of a diagnostic test for the effectiveness of treatment given diabetic patients. Some believe that further reactions of the glucosylated proteins yield products that lead to development of some of the complications of diabetes mellitus. My research interest in this area includes: 1. identification of the actual products formed by reaction of glucosylated proteins; 2. study of the mechanism of browning reactions, currently emphasizing a study of possible free radical involvement; 3. determination of the kinetics by which various Maillard reactions occur, which will inform the development of a computer simulation of protein browning over long time periods under physiological conditions.

Natural products: I intend to develop a program for finding undiscovered terpenes, peptides, polysaccharides, and other natural products produced by native fauna and flora. This project will involve isolation of compounds by differential extractions and chromatography, testing them for pharmaceutical potential, and identifying their structures by NMR and other forms of spectroscopy.

Selected Publications

  1. C. A. Ng, W. Zhao, J. Dang, M. Bergdahl, F. Separovic, R. T. C. Brownlee, and R. P. Metzger, "The Conformation of Acetylated Virginiamycin M1 and Virginiamycin M1 in Explicit Solvents." Biochim. Biophys. Acta 1774, 2006 610-618.
  2. R. P. Metzger, "Thoughts on the teaching of metabolism," Biochem. Molec. Bio. Educ. 34, 2006 78-87.
  3. J. Dang, R. P. Metzger, R.T.C. Brownlee, C. A. Ng, M. Bergdahl and F. Separovic, "The conformational flexibility of the antibiotic Virginiamycin M1," Eur. Biophys. J. 34, 2005 383-388.
  4. J. L. Lord, A. de Peyster, P. J. E. Quintana, and R. P. Metzger, "Cytotoxicity of Xanthopterin and Isoxanthopterin in MCF-7 Cells," Cancer Lett. 222, 2005 119-124.
  5. J. Dang, F. Separovic, B. M. Bergdahl, R. T. C. Brownlee and R. P. Metzger, "Solvent Affects the Conformation of Virginiamycin M1 (Pristinamycin IIA, Streptogramin A)," Org. Biomol. Chem. 2, 2004 2919-2924.
  6. J. Dang; B.M. Bergdahl; F. Separovic; R.T.C. Brownlee; R.P. Metzger, "Virginiamycin M1 Conformation in Solution Differs From the Form Bound to the 50S Ribosome and to Streptogramin Acetyltransferase," Aust. J. Chem. 2004 415.
  7. D.F. Shellhamer, O. Sharts, V.S. Gorelik, et al., "Applications of quantitative pulsed laser isochronic Raman spectrometer detection of carbon-fluorine bonds in gases, solids, suspensions, and solutions," Am. Lab. Suppl. 2002 32.