Nanosecond electric pulses deprive zinc ions of carboxypeptidase G2

Nanosecond electric pulses (nsEP, 10 kV/cm with a pulse duration of 8, 16 or 24 ns) inhibited the activity of carboxypeptidase G2 (CPG2), a zinc-dependent homodimer; the relative activity was <20% when the total exposure time was >120 S. No alterations were detected in electrophoresis, chromatography, mass spectroscopy and circular dichroism, thus demonstrating intactness of the apoenzyme. Inductively coupled plasma-mass spectrometry indicated that zinc levels were 330 mu g/mg protein in control CPG2, and decreased to 0.40, 0.12 or 038 mu g/mg protein after 240 s of 8-, 16- or 24-ns pulses, respectively. In CPG2 exposed to 240 s of 8-, 16- and 24-ns pulses, the reloading of zinc with redialysis recovered the activity to 94.7 +/- 3.4%, 84.0 +/- 5.2% and 81.7 +/- 7.0%, respectively (p = 0.0853, 0.0741, 0.0668). These data demonstrated that nsEP inhibited CPG2 via removal of zinc, and that nsEP can be used to modulate CPG2. (C) 2014 Elsevier B.V. All rights reserved.