Aminopeptidase B (EC 3.4.11.6)

Aminopeptidase B (EC 3.4.11.6) is a Zn2+-dependent exopeptidase which selec tively removes arginine and/or lysine residues from the NH2-terminus of sev eral peptide substrates including Arg(0)-Leu-enkephalin, Arg(0)-Met-enkepha lin and Arg(-1)-Lys(0)-somatostatin-14. Analysis of its primary structure s howed that aminopeptidase-B is structurally related to leukotriene A(4) hyd rolase, an important enzyme of the arachidonic acid pathway. This structura l relationship is further supported by the capacity of aminopeplidase-B to hydrolyse leukotriene A(4). Aminopeptidase-B is widely distributed in a num ber of tissues, including endocrine and non-endocrine cells. Moreover, in r at PC12 pheochromocytoma cells, the enzyme is secreted and associated with the external face of the plasma membrane. Together these data strongly argu e in favour of a role of this bi-functional enzyme in the final stages of p recursor processing mechanisms occurring either in the secretory pathway, a t the plasma membrane, or at both locations. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.