Extracellular aminopeptidase that allows assimilation of proteinaceous substrates. Binds 2 Zn(2+) ions per subunit. Calcium, magnesium and manganese cations reduce peptidase activity to 20.3-51.3 percent. The metal ion chelating reagent EDTA almost completely inhibits activity. The protease inhibitor bacitracin and the aminopeptidase B inhibitor bestatin, as well as DTT and beta-mercaptoethanol act also as lap A inhibitorsD. Optimum pH is 8.5. Optimum temperature is 60 degrees Celsius. Monomer. Expressed at higher level at alkaline conditions. May be under the control of pacC, the transcription factor that regulates pH-conditional gene expression. Expression is very low under normal condition, salt condition and heat-stress condition. Belongs to the peptidase M28 family. M28E subfamily.