Aminopeptidase B (EC 3.4.11.6)

Aminopeptidase B (EC 3.4.11.6) is a Zn2+-dependent exopeptidase which selectively removes arginine and/or lysine residues from the NH2-terminus of several peptide substrates including Arg(0)-Leu-enkephalin, Arg(0)-Met-enkephalin and Arg(-1)-Lys(0)-somatostatin-14. Analysis of its primary structure showed that aminopeptidase-B is structurally related to leukotriene A(4) hydrolase, an important enzyme of the arachidonic acid pathway. This structural relationship is further supported by the capacity of aminopeplidase-B to hydrolyse leukotriene A(4). Aminopeptidase-B is widely distributed in a number of tissues, including endocrine and non-endocrine cells. Moreover, in rat PC12 pheochromocytoma cells, the enzyme is secreted and associated with the external face of the plasma membrane. Together these data strongly argue in favour of a role of this bi-functional enzyme in the final stages of precursor processing mechanisms occurring either in the secretory pathway, at the plasma membrane, or at both locations. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.