title: Acid-induced unfolding kinetics in simulated gastric digestion of proteins.
abstract: Stability in simulated gastric fluid (SGF) is used as one element in a weight-of-evidence evaluation aimed at determining if a novel protein present in food represents an allergenic risk. The SGF assay is designed to measure the susceptibility of a protein to the enzyme pepsin under acidic conditions, and results are often considered to be primarily a reflection of the vulnerability of a protein to pepsin hydrolysis. However, proteins may not be susceptible to protease cleavage in their native folded conformation, and several studies confirm that protein unfolding is often a prerequisite for pepsinolysis. Here, we explore protein unfolding kinetics as a limiting factor in the digestion of proteins in SGF. Theoretical digestion patterns generated using consecutive and simultaneous exponential models, and the fit of a two stage consecutive exponential model (unfolding followed by pepsinolysis) to laboratory data, support unfolding kinetics as playing a critical role in determining the speed at which many proteins digest in SGF. Results also support modeling of the terminal phase of digestion with a single exponential decline as being a good stability estimate for the most recalcitrant protein form.
authors.affiliation: Dow AgroSciences LLC, 9330 Zionsville Road, Indianapolis, IN 46268, USA. raherman@dow.com
authors.forename: Rod
authors.initials: R
authors.lastname: Herman
authors.forename: Yong
authors.initials: Y
authors.lastname: Gao
authors.forename: Nicholas
authors.initials: N
authors.lastname: Storer
mesh_terms: D004063:Digestion / Q000502:physiology*; D005744:Gastric Acid / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D017510:Protein Folding; D011506:Proteins / Q000378:metabolism*
chemical_list: D011506:Proteins