Characterization of Ghrelin O-acyltransferase Active Site

Ghrelin, first discovered in 1999, is a 28-amino acid peptide hormone involved in the regulation of appetite, insulin secretion and sensitivity, and many neurological effects such as learning, memory, and depression.1-6 Ghrelin has been identified to have a unique posttranslational octanoylation carried out by the enzyme ghrelin O-acyltransferase (GOAT). This distinctive modification is a point of interest in studying GOAT whereby blocking the acylation of the ghrelin could potentially halt the activity of the peptide hormone and provide a means of treating obesity, diabetes, and other diseases affected by ghrelin levels. The duration of my project involved working with a 20-amino acid mimic of the ghrelin peptide with various single residue mutations in the original wild type ghrelin sequence (GSSFLSPEHQRVQQRKESKK). The 20-amino acid ghrelin mimics are fluorescently labeled with a single acrylodan compound, and the activity as well as the inhibitory effects are monitored via reverse phase high performance liquid chromatography.7 Further studies were done to identify the interactions of ghrelin with GOAT specifically at the N-terminal lysine-5 position of ghrelin. Defining the interactions of ghrelin with the GOAT binding site and octanoyl Co-A substrates would pave the way to design inhibitors and aid in helping diseases related to diabetes, obesity, and neurological illnesses such as Alzheimer’s and Parkinson’s.