Dr. Allen Phillips
Emeritus Professor of Biochemistry
Department: Biochemistry and Molecular Biology
College: Eberly College of Science
Address: 203A South Frear Building
Phone: 814-865-1247
E-mail: atp@psu.edu
Website: http://www.personal.psu.edu/faculty/a/t/atp/
Enzymology and regulation of amino acid metabolismOur interests center on control of the synthesis and activity of enzymes involved in the metabolism of the amino acid histidine. These studies include regulation of enzyme activity and gene expression, mechanisms of coenzyme function, and structure-function analysis of the proteins required for histidine breakdown. Several of the pathway’s enzymes are known to be reduced or absent in the human genetic disorders histidinemia and urocanic acidemia, respectively, and thus an understanding of these enzymes and their regulation could prove useful in overcoming the consequences of their deficiency. Currently we are focused on urocanase, the second of five enzymes in the pathway, plus the repressor protein which controls expression of all histidine utilization genes including that for a specialized histidine transporter. Using a bacterial model system because all organisms metabolize histidine by a mostly common pathway, we seek to examine the nature of NAD binding to urocanase in order to better understand the extremely tight binding exhibited between the enzyme’s protein and NAD, and how NAD functions in this unusual non-redox reaction process. In addition to NAD’s function in urocanase, we also are exploring a possible role for NAD in an urocanic acid isomerase found in Micrococcus luteus which promotes the sunlight-induced interconversion of urocanic acid’s two isomeric forms (cis and trans). The cis-isomer is well documented as an immunosuppressive agent in skin tissue, an area often associated with M. luteus in humans.
Our work at the gene regulation level primarily concerns characterizing the repressor protein for the hut regulon in Pseudomonas putida and determining the locations and sequence of the various operator regions recognized by the repressor in order to understand if the repressor’s binding to two chemically distinct inducers (urocanate and N-formylglutamate) leads to selectivity in gene expression. Additionally, a yet-uncharacterized gene co-transcribed with the hut repressor gene is being studied for its possible role in directing the repressor’s action. In addition to histidine’s breakdown, we are also involved in a study of its conversion to ergothioneine (EGT), a histidine derivative produced only by some fungi and a few bacteria. EGT is believed to be a unique type of antioxidation agent important in controlling oxygen damage associated with the aging process. Humans produce no EGT but obtain it from food sources; therefore our efforts are currently directed towards elevating EGT content in mushrooms, one of the most common food sources of EGT.
Previous WISER, MURE, and FURP students working here have gained experience with many biochemical research techniques as they conducted studies on growth of recombinant microbes , expression of cloned genes, purification of enzymes, measurement of enzyme activity, characterization of protein properties, gene sequence modification and protein-DNA binding. In addition to mastery of essential biochemical and microbiological techniques, they also learned how research is conducted, including experimental design, data collection, data analysis, and interpretation of results. For most, this has solidified their interest in pursuing a career in science and technology areas.