May 2, 2016

Did you know that high fructose corn syrup is made from cornstarch by converting glucose into fructose? This conversion is possible thanks to the amazing glucose isomerase, which is found in many species of bacteria. (Unfortunately organic chemistry was never forte but I tried to understand the process.) When the glucose enters the active site of the enzyme, a histidine residue catalyzes a proton transfer to an oxygen molecule. After gaining the positive hydrogen, the oxygen breaks its bond with a carbon. The carbon then creates a pi bond with another oxygen, forming an open chain. The metals in the enzyme catalyze a hydride shift creating a carbocation. The resonance structure allows the sugar to become an enol. However enols are reactive and will react with surrounding water molecules, leading up to fructose.