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
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