Activity/stability of human pepsin: implications for reflux attributed laryngeal disease. Laryngoscope 2007 Jun;117(6):1036-9
Date
04/10/2007Pubmed ID
17417109DOI
10.1097/MLG.0b013e31804154c3Scopus ID
2-s2.0-34249873017 (requires institutional sign-in at Scopus site) 215 CitationsAbstract
OBJECTIVES/HYPOTHESIS: Exposure of laryngeal epithelia to pepsin during extra-esophageal reflux causes depletion of laryngeal protective proteins, carbonic anhydrase isoenzyme III (CAIII), and squamous epithelial stress protein Sep70. The first objective of this study was to determine whether pepsin has to be enzymatically active to deplete these proteins. The second objective was to investigate the effect of pH on the activity and stability of human pepsin 3b under conditions that might be found in the human esophagus and larynx.
STUDY DESIGN: Prospective translational research study.
METHODS: An established porcine in vitro model was used to examine the effect of active/inactive pepsin on laryngeal CAIII and Sep70 protein levels. The activity and stability of pepsin was determined by kinetic assay, measuring the rate of hydrolysis of a synthetic pepsin-specific substrate after incubation at various pH values for increasing duration.
RESULTS: Active pepsin is required to deplete laryngeal CAIII and Sep70. Pepsin has maximum activity at pH 2.0 and is inactive at pH 6.5 or higher. Although pepsin is inactive at pH 6.5 and above, it remains stable until pH 8.0 and can be reactivated when the pH is reduced. Pepsin is stable for at least 24 hours at pH 7.0, 37 degrees C and retains 79% +/- 11% of its original activity after re-acidification at pH 3.0.
CONCLUSIONS: Detectable levels of pepsin remain in laryngeal epithelia after a reflux event. Pepsin bound there would be enzymatically inactive because the mean pH of the laryngopharynx is pH 6.8. Significantly, pepsin could remain in a form that would be reactivated by a subsequent decrease in pH, such as would occur during an acidic reflux event or possibly after uptake into intracellular compartments of lower pH.
Author List
Johnston N, Dettmar PW, Bishwokarma B, Lively MO, Koufman JAAuthor
Nikki Johnston PhD Professor in the Otolaryngology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Blotting, WesternEsophagoscopy
Gastric Acid
Gastroesophageal Reflux
HSP70 Heat-Shock Proteins
Humans
Hydrogen-Ion Concentration
Laryngeal Diseases
Laryngeal Mucosa
Pepsin A
Prospective Studies