Specific interaction of cytosolic and mitochondrial glyoxalase II with acidic phospholipids in form of liposomes results in the inhibition of the cytosolic enzyme only

Kinetics of cytosolic recombinant human glyoxalase II and bovine liver mito chondrial glyoxalase II mere studied in the presence of liposomes made of d ifferent phospholipids (PLs). Neutral PLs such as egg phosphatidylcholine o r dipalmitoylphosphatidylcholine did not affect the enzymatic activity of e ither enzymatic form. Liposomes made of dioleoyl phosphatidic acid or cardi olipin or phosphatidylserine also did not affect the enzymatic activity of mitochondrial glyoxalase II. Conversely, these negatively charged PLs exert ed noncompetitive inhibition on cytosolic glyoxalase II only, dioleoyl phos phatidic acid and bovine brain phosphatidylserine exerting the highest and lowest inhibition, respectively. Binding studies, carried out by using a re sonant mirror biosensor, revealed that liposomes made of negatively charged PLs interact specifically with both enzymatic forms of glyoxalase II, wher eas interactions were not detected with neutral PLs. Once bound on glyoxala se II, negatively charged liposomes could not be removed by 3 M NaCl, sugge sting that interactions between glyoxalase II and negatively charged PLs, b esides ionic, may be also hydrophobic. These data suggest a possible role of negatively charged phospholipids in t he regulation of level of lactoylglutathione in the cell. The data are also discussed in terms of a possible regulation of reduced glutathione supply to mitochondria, Proteins 2000;41:33-39. (C) 2000 Wiley Liss, Inc.