Metal ion substitution in the catalytic site greatly affects the binding of sulfhydryl-containing compounds to leucyl aminopeptidase.
Bovine lens leucyl aminopeptidase (blLAP), a homohexameric metallopeptidase preferring bulky and hydrophobic amino acids at the N-terminus of (di)peptides, contains two Zn(2+) ions per subunit that are essential for catalytic activity. They may be replaced by other divalent cations with different exchange kinetics. The protein readily exchangeable site (site 1) can be occupied by Zn(2+), Mn(2+), Mg(2+), or Co(2+), while the tight binding site (site 2) can be occupied by Zn(2+) or Co(2+). We recently reported that introduction of Mn(2+) into site 1 generates a novel activity of blLAP toward CysGly [Cappiello, M., et al. (2004) Biochem. J. 378, 35-44], which in contrast is not hydrolyzed by the (Zn/Zn) enzyme. This finding, while disclosing a potential specific role for blLAP in glutathione metabolism, raised a question about the features required for molecules to be a substrate for the enzyme. To clarify the interaction of the enzyme with sulfhydryl-containing derivatives, (Zn/Zn)- and (Mn/Zn)blLAP forms were prepared and functional-structural studies were undertaken. Thus, a kinetic analysis of various compounds with both enzyme forms was performed; the crystal structure of (Zn/Zn)blLAP in complex with the peptidomimetic derivative Zofenoprilat was determined, and a modeling study on the CysGly-(Zn/Zn)blLAP complex was carried out. This combined approach provided insight into the interaction of blLAP with sulfhydryl-containing derivatives, showing that the metal exchange in site 1 modulates binding to these molecules that may result in enzyme substrates or inhibitors, depending on the nature of the metal.
Cappiello
Mario
M
Department of Physiology and Biochemistry, University of Pisa, I-56126 Pisa, Italy.
Alterio
Vincenzo
V
Amodeo
Pietro
P
Del Corso
Antonella
A
Scaloni
Andrea
A
Pedone
Carlo
C
Moschini
Roberta
R
De Donatis
Gian Marco
GM
De Simone
Giuseppina
G
Mura
Umberto
U
D001665:Binding Sites; D020134:Catalytic Domain; D002413:Cations, Divalent / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D006867:Hydrolases / Q000378:metabolism; D007700:Kinetics; D007931:Leucyl Aminopeptidase / Q000737:chemistry / Q000378:metabolism*; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D008958:Models, Molecular; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism*; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology
D002413:Cations, Divalent; D004791:Enzyme Inhibitors; D013438:Sulfhydryl Compounds; D008345:Manganese; D006867:Hydrolases; D007931:Leucyl Aminopeptidase; D015032:Zinc