Conformational Changes of Phenylalanine Dehydrogenase in the Presence of Ionic Gold and Alkaline pH

Document Type : Article


1 Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Department of Life Science Engineering, Faculty of New Sciences & Technologies, University of Tehran, Tehran, Iran

3 Department of Interdisciplinary Technologies, Breast Cancer Research Center, Biomaterials and Tissue Engineering Research Group, Motamed Cancer Institute, ACECR, Tehran, Iran

4 Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran


Phenylalanine dehydrogenase (PheDH) is an important enzyme for determining the serum L-phenylalanine levels to diagnose phenylketonuria (PKU) disease. PheDH enzyme catalyzes the reversible oxidative deamination of L-phenylalanine to phenylpyruvate in the presence of NAD+ as a cofactor. In this study, recombinant histidine-tailed Bacillus badius PheDH was expressed and purified by Ni-Sepharose affinity chromatography column. The kinetic properties of the native enzyme such as Km, kcat, Vmax and kcat/Km values for L-Phenylalanine and NAD+ substrates in the oxidative deamination reaction were determined. Then the effects of the gold salt and pH on the enzyme tertiary structure and enzyme activity was assayed using UV-Vis and fluorescence spectroscopy. The activity was decreased in the presence of certain concentrations of gold compared to the native enzyme. Also the results showed that gold or high pH (~12.5) affects the tertiary structure of the PheDH enzyme, because intrinsic fluorescence emission at 340 nm decreased for native enzyme in their presence