1.Identification of glutamic acid 646 as a zinc-coordinating residue in endopeptidase-24.11.
Le Moual H1, Devault A, Roques BP, Crine P, Boileau G. J Biol Chem. 1991 Aug 25;266(24):15670-4.
Neutral endopeptidase (EC 3.424.11, NEP) is a membrane-bound zinc-metallopeptidase. The substrate specificity and catalytic activity of NEP resemble those of thermolysin, a bacterial zinc-metalloprotease. Comparison of the primary structure of both enzymes suggests that several amino acids present in the active site of thermolysin are also found in NEP. Using site-directed mutagenesis of the cDNA encoding the NEP sequence, we have already shown that His residues 583 and 587 are two of the three zinc ligands. In order to identify the third zinc ligand, we have substituted Val or Asp for Glu616 or Glu646. Val616 NEP showed the same kinetic parameters as the non-mutated NEP. In contrast, the mutant Val646 NEP was almost completely devoid of catalytic activity and unable to bind the tritiated inhibitor [3H]N-[2(R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxypropyl]gl ycine, the binding of which is dependent on the presence of the zinc ion. Replacing Glu for Asp at position 646 conserved the negative charge, and the mutant enzyme exhibited the same Km value as the non-mutated enzyme, but kCat was decreased to less than 3% of the value of the non-mutated enzyme.
2.Crystal structure of leukotriene A4 hydrolase in complex with kelatorphan, implications for design of zinc metallopeptidase inhibitors.
Tholander F1, Roques BP, Fournié-Zaluski MC, Thunnissen MM, Haeggström JZ. FEBS Lett. 2010 Aug 4;584(15):3446-51. doi: 10.1016/j.febslet.2010.06.044. Epub 2010 Jul 4.
Leukotriene A4 hydrolase (LTA4H) is a key enzyme in the inflammatory process of mammals. It is an epoxide hydrolase and an aminopeptidase of the M1 family of the MA clan of Zn-metallopeptidases. We have solved the crystal structure of LTA4H in complex with N-[3(R)-[(hydroxyamino)carbonyl]-2-benzyl-1-oxopropyl]-L-alanine, a potent inhibitor of several Zn-metalloenzymes, both endopeptidases and aminopeptidases. The inhibitor binds along the sequence signature for M1 aminopeptidases, GXMEN. It exhibits bidentate chelation of the catalytic zinc and binds to LTA4H's enzymatically essential carboxylate recognition site. The structure gives clues to the binding of this inhibitor to related enzymes and thereby identifies residues of their S1' sub sites as well as strategies for design of inhibitors.
3.Studies of the biogenic amine transporters. VI. Characterization of a novel cocaine binding site, identified with [125I]RTI-55, in membranes prepared from whole rat brain minus caudate.
Rothman RB1, Silverthorn ML, Baumann MH, Goodman CB, Cadet JL, Matecka D, Rice KC, Carroll FI, Wang JB, Uhl GR, et al. J Pharmacol Exp Ther. 1995 Jul;274(1):385-95.
Previous studies showed that the cocaine analog [125I]RTI-55 labels dopamine and serotonergic (5-HT) biogenic amine transporters (BATs) with high affinity. Here we characterized [125I]RTI-55 binding to membranes prepared from whole rat brain minus the caudate nuclei. Paroxetine (50 nM) was used to block [125I]RTI-55 binding to 5-HT transporter sites. Initial experiments identified drugs that displaced [125I]RTI-55 binding with moderately low slope factors. Binding surface analysis of the interaction of 3 beta-(4-chlorophenyl)tropan-2 beta-carboxylic acid phenyl ester hydrochloride (RTI-113) and 3 beta-(4-iodophenyl)tropan-2 beta-carboxylic acid phenyl ester hydrochloride (RTI-122) with [125I]RTI-55 binding sites readily resolved two binding sites for [125I]RTI-55 with Kd values of 0.44 nM and 17 nM and Bmax values of 31 and 245 fmol/mg protein. Potent 5-HT and noradrenergic uptake inhibitors had low affinity for both sites. Whereas cocaine, CFT and WIN35,065-2 were 6.
4.2-substituted-1-naphthols as potent 5-lipoxygenase inhibitors with topical antiinflammatory activity.
Batt DG1, Maynard GD, Petraitis JJ, Shaw JE, Galbraith W, Harris RR. J Med Chem. 1990 Jan;33(1):360-70.
The synthesis, biological evaluation, and structure-activity relationships of a series of 1-naphthols bearing carbon substituents at the 2-position are described. These compounds are potent inhibitors of the 5-lipoxygenase from RBL-1 cells and also inhibit bovine seminal vesicle cyclooxygenase. Structure-activity relationships for these two enzymes are different, implying specific enzyme inhibition rather than a nonspecific antioxidant effect. 2-(Aryl-methyl)-1-naphthols are among the most potent 5-lipoxygenase inhibitors reported (IC50 values generally 0.01-0.2 microM) and show excellent antiinflammatory potency in the mouse arachidonic acid ear edema model. To study the effects of structure on in vitro and in vivo activity, four general features of the molecules were varied: the 2-substituent, the 1-hydroxyl group, substitution on the naphthalene rings, and the 1,2-disubstituted naphthalene unit itself. 2-Benzyl-1-naphthol (5a, DuP 654) shows a very attractive profile of topical antiinflammatory activity and is currently in clinical trials as a topically applied antipsoriatic agent.