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NameManuela Marin Salcedo
TopicBiochemistry / Chem Bio.

The Effect of Novel Ionic Liquids on the Enzyme Catalysis of Histidase


Charles H. Wallace, Manuela Marin Salcedo, Brandon G. Maier, Kammie M. Conrad, Michael D. King

Author Location(s)

Florida Gulf Coast University, Fort Myers, FL


Histidase, an enzyme found in skin, reacts with histidine to form trans-urocanic acid. Ionic liquids (ILs) are an intriguing class of tunable, environmentally-friendly solvents whose physiochemical properties make them important media for the stabilization and activation of enzymes. The ILs used in this study can be classified as Protic, Aprotic and novel Protic-Aprotic. Protic Ionic Liquids (PILs) possess a positively-charged Hydrogen available for donation while Aprotic Ionic Liquids (AILs) do not. The novel Protic-Aprotic liquids, or Bridged Ionic Liquids (BILs), possess the two distinct extremes. This project aims to use PILs, BILs and AILs as a probe into investigating their effect on the enzyme catalysis of Histidase, using an ultraviolet-visible spectrophotometer (Model Shimadzu UV 2450) with a temperature-controlled cell holder (Model TCC240) to measure the formation of trans-urocanic acid at 277 nm. Vmax and Km were determined through non-linear regression (Dynafit) of the Michaelis-Menten plot, and type of inhibition will be determined using linear regression of a Dixon plot. Triplicate runs of five different concentrations of histidine with three different concentrations of each IL were used. BIL 3 produced little effect on catalytic activity whereas BILs 1, 2, and 4 exhibited an increase in inhibition. BIL 5 produced a large decrease in catalytic activity. Thus far, all PILs inhibit enzyme activity though PIL 3 inhibits more than PIL 2 which inhibits more than PIL 1. The Km and Vmax of the inhibitors were compared to a “baseline” which did not include any IL.