title: Substrate-induced intramolecular proton transfer in 6-phosphogluconate dehydrogenase from Candida utilis.
abstract: Formation of binary complex between 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate:NADP+ 2-oxidoreductase (decarboxylating), EC 1.1.1.44) from Candida utilis and 6-phosphogluconate was investigated by means of ultraviolet difference spectroscopy. The formation of the enzyme-substrate complex induces in the difference spectrum a positive peak the wavelength and extinction coefficient of which agree well with a tyrosine ionization. Titrimetric studies indicate that the formation of the binary complex is not coupled to a proton release from the protein. These data support an intramolecular proton transfer from a tyrosine to other functional group. This proton transfer could be correlated to the conformational change induced by substrate in 6-phosphogluconate dehydrogenase.
mesh_terms: D002175:Candida / Q000201:enzymology*; D005942:Gluconates / Q000378:metabolism; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism*; D011487:Protein Conformation; D011522:Protons; D013056:Spectrophotometry, Ultraviolet; D013403:Sugar Phosphates / Q000378:metabolism
chemical_list: D005942:Gluconates; D011522:Protons; D013403:Sugar Phosphates; D010734:Phosphogluconate Dehydrogenase; C008884:6-phosphogluconic acid