Ubiquitin Causes Selective Increase in the Sensitivity of Rat Brain Mitochondrial Monoamine Oxidases to Various Proteases

摘要

Incubation of rat brain mitochondria with ubiquitin and ATP followed by subsequent mitochondriasedimentation was accompanied by reduction of ubiquitin content in the supernatant. This decrease was morepronounced in the presence of ATP-regenerating system in the incubation medium (creatine phosphate/creatinephosphokinase). This ubiquitin incorporation into brain mitochondria observed only in the presence of ATP inthe incubation medium increased sensitivity of monoamine oxidases (MAO) A and B to proteolytic inactivationby trypsin and papain, respectively. (Ubiquitin did not influence sensitivity of MAO B to trypsin and MAO Ato papain). The data obtained suggest that ubiquitin incorporation into rat brain mitochondria increases suscep-tibility of MAOs to certain exogenous proteases, however, it remains unclear whether these changes stem fromdirect MAO-ubiquitin conjugation or reflect alterations in the membrane environment of these enzymes.