부산대학교 도서관

Leucine aminopeptidase belongs to the metallohydrolase family M17. In this family, two X‐ray diffraction structures are known for bovine lens LAP (blLAP) and for the Escherichia coli aminopeptidase A (PepA). These two peptidases are large homohexamers of 32 symmetry, and both have a large central solvent cavity near the active sites. Each active center contains two Zn2+ separated by 3.0 Å. In PepA, maximal activity occurs in the presence of Mn2+. blLAP is activated by Mn2+, Mg2+ or Co2+, but zinc is bound most strongly and is supposed to be the physiological cofactor. In the proposed catalytic mechanism, both metal ions stabilize substrate binding and formation of the transition state. In addition, a lysine side chain contributes by polarizing the substrate's carbonyl group, and an arginine side chain binds a bicarbonate anion (or carbonate ion) that is in a position to act, at least in PepA, as a general base to deprotonate the zinc‐bound water nucleophile.
3D Structure View of the blLAP protomer structure (PDB id 1LAM). The catalytic C‐terminal domain is colored in red and the N‐terminal domain in green. The two zinc ions are shown in yellow. This figure has been prepared using programs MOLSCRIPT and RASTER3D.