REDOX POTENTIAL OF THE HEME-C GROUP IN THE QUINOCYTOCHROME, LUPANINE HYDROXYLASE, AN ENZYME LOCATED IN THE PERIPLASM OF A PSEUDOMONAS SP

The quinocytochrome c, lupanine hydroxylase, was shown to be located i n the periplasm of a Pseudomonas sp. The midpoint redox potential of t he haem In the purified enzyme was measured by potentiometric titratio n and shown to be +193 mV. PQQ was removed from the enzyme by isoelect ric focusing to give inactive apoenzyme. This resulted in a shift in t he midpoint redox potential of the haem to +98 mV. Full activity was r ecovered by the addition of PQQ to apoenzyme that also restored the or iginal potential. (C) 1998 Elsevier Science B.V.