Mariah Pierce

Date of Award

9-13-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

James Hougland

Subject Categories

Chemistry | Physical Sciences and Mathematics

Abstract

Ghrelin is an octanoylated peptide hormone that is active in a multitude of pathways that contribute to appetite simulation, glucose homeostasis, growth hormone secretion, and insulin secretion. To activate its cognate receptor, ghrelin must be acylated by octanoic acid on a serine side chain. The enzyme responsible for this functional modification is ghrelin O-acyltransferase (GOAT). GOAT is part of the mammalian membrane bound O-acyltransferase (MBOAT) family. Understanding GOAT’s acylation mechanism could lead to promising areas for pharmaceutical development by modulation of ghrelin signaling. Based on the published inhibitors of GOAT we propose involvement of a catalytic side chain hydroxyl in GOAT’s mechanism. Here I assess the involvement of an activated serine hydroxyl in GOAT and present new potent hGOAT inhibitors. hGOAT has been shown to be incredibly difficult to purify due to lack of stability outside of its lipid membrane environment. Using detergents to mimic the lipid membrane, we present the first solubilized, purified, and active hGOAT. Continuing ghrelin’s maturation, it is secreted and deacylated in the bloodstream by one or more circulating esterases which inactivates the peptide. Among the possible esterases responsible for ghrelin deacylation, the secreted esterase Notum has been shown to deacylate Wnt proteins through hydrolysis of a similar serine ester linkage. Determining if human Notum (hNotum) deacylates ghrelin begins with expression and purification of hNotum to enable development of an in vitro ghrelin deacylation assay can begin.

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Open Access

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