HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 569/2/419    most recent jphysiol.2005.094748v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Morgan, D. Articles by DeCoursey, T. E. Search for Related Content PubMed PubMed Citation Articles by Morgan, D. Articles by DeCoursey, T. E.

¹ Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 West Harrison, Chicago, IL 60612, USA
² Department of Pediatrics, Northwestern University Feinberg School of Medicine, Children's Memorial Hospital, Division of Infectious Diseases, 2300 Children's Plaza, Chicago, IL 60614, USA

NADPH oxidase generates reactive oxygen species that are essential to innate immunity against microbes. Like most enzymes, it is sensitive to pH, although the relative importance of pH_o and pH_i has not been clearly distinguished. We have taken advantage of the electrogenic nature of NADPH oxidase to determine its pH dependence in patch-clamped individual human eosinophils using the electron current to indicate enzyme activity. Electron current stimulated by PMA (phorbol myristate acetate) was recorded in both perforated-patch configuration, using an NH₄₊ gradient to control pH_i, and in excised, inside-out patches of membrane. No electron current was detected in cells or excised patches from eosinophils from a patient with chronic granulomatous disease. When the pH was varied symmetrically (pH_o= pH_i) in cells in perforated-patch configuration, NADPH oxidase-generated electron current was maximal at pH 7.5, decreasing drastically at higher or lower values. Varying pH_o and pH_i independently revealed that this pH dependence was entirely due to effects of pH_i and that the oxidase is insensitive to pH_o. Surprisingly, the electron current in inside-out patches of membrane was only weakly sensitive to pH_i, indicating that the enzyme turnover rate per se is not strongly pH dependent. The most likely interpretation is that assembly or deactivation of the NADPH oxidase complex has one or more pH-sensitive steps, and that pH-dependent changes in electron current in intact cells mainly reflect different numbers of active complexes at different pH.

(Received 14 July 2005; accepted after revision 23 September 2005; first published online 29 September 2005)
Corresponding author T. E. DeCoursey: Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 West Harrison, Chicago, IL 60612, USA. Email: tdecours{at}rush.edu

This article has been cited by other articles:

				Errata J. Physiol., January 15, 2006; 570(2): 429 - 429. [Full Text] [PDF]