The proteolytic activity of insulin-degrading enzyme: a mass spectrometry study

The prominent role that insulin-degrading enzyme (IDE) has on amyloidogenic peptides degradation has recently boosted a lot of attention toward this enzyme. Although many substrates are known to be degraded by IDE, little is known about the changes in the proteolytic activity of the enzyme upon modification of environmental factors. In a previous work we have already shown the great potentiality of atmospheric pressure/laser desorption ionization-mass spectrometry (AP/MALDI-MS) for studying the interaction between IDE and insulin. Here, the activity of IDE was investigated regarding cleavage sites' preferentiality upon modification of environmental factors by AP/MALDI-MS. The roles that IDE/insulin concentration ratio, reaction time, adenosine 5'-triphosphate (ATP) and metal ions (Zn and Cu) have on the insulin cleavage pattern produced by IDE are investigated and a plausible interpretation involving the proteolytic action of the different IDE oligomeric forms is proposed.