A drug-unresponsive and protease-resistant CNOX protein from human sera

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ammonium sulf ate fractionation were employed in series to purify and concentrate a 12.5- kDa protein fragment with a periodic (24-min period) proteinase K-resistant and drug-unresponsive NADH oxidase (CNOX) activity from pooled sera from h ealthy volunteers. The activity was unresponsive to capsaicin to distinguis h it from the previously isolated cancer-associated NOX form (tNOX), Polycl onal antisera generated to the CNOX fragment cross-reacted with 20.5- to 24 -kDa proteins of human sera, human lymphocytes, and plasma membranes from E scherichia coli with the molecular weight depending on source and condition s of treatment with proteinase K. (C) 2001 Academic Press.