Conformationally constrained analogues of endogenous tripeptide inhibitors of zinc metalloproteinases.

Two diastereomeric furan-2-carbonylamino-3-oxohexahydroindolizino[8,7-b]indole carboxylates, highly constrained analogues of endogenous pyroglutamyl tripeptide inhibitors of snake venom endopeptidases, have been prepared as potential inhibitors of adamalysin II and matrix metalloproteinases. They proved to be inactive against adamalysin II and weak inhibitors of gelatinase A, gelatinase B, stromelysin 1 and human neutrophil collagenase. Evaluation of the mode of binding of the (2R,5S,11bR) isomer in the active site of adamalysin II suggests that the decrease of potency may be due to the reorientation of the acylamino chain in three of the heterocyclic nucleus, to a short contact at the entrance of the S'(1) hydrophobic cleft and to the loss of flexibility of the tetracyclic nucleus in the P'(1), P'(2) region of the inhibitor, which prevents optimal arrangement in the S'(1) specificity subsite.

Two crystal structures of human neutrophil collagenase, one complexed with a primed- and the other with an unprimed-side inhibitor: implications for drug design.

Two crystal structures of human neutrophil collagenase (HNC, MMP-8), one complexed with a primed- and the other with an unprimed-side inhibitor, were determined using synchrotron radiation at 100 K. Both inhibitors contain non-hydroxamate zinc-binding functions. The Pro-Leu-L-Trp(P)(OH)(2) occupies the unprimed region of the active site, furnishes new structural information regarding interaction between the catalytic zinc ion and the phosphonate group, and is the only example of occupation of the S(1) subsite of MMP-8 by the bulky tryptophan side chain. The (R)-2-(biphenyl-4-ylsulfonyl)-1,2,3, 4-tetrahydroisochinolin-3-carboxylic acid, a conformationally constrained D-Tic derivative, accommodates its biphenyl substituent into the deep primary specificity S(1)' subsite, inducing a widening of the entrance to this pocket; this modification of the protein, mainly consisting in a shift of the segment centered at Pro217, is observed for the first time in MMP-8 complexes. Cation-aromatic interactions can stabilize the formation of both complexes, and the beneficial effect of aromatic substituents in proximity of the catalytic zinc ion is discussed. The phosphonate group bound to either a primed- or unprimed-side inhibitor maintains the same relative position with respect to the catalytic zinc ion, suggesting that this binding function can be exploited for the design of combined inhibitors assembled to interact with both primed and unprimed regions of the active cleft.

Inhibition of adamalysin II and MMPs by phosphonate analogues of snake venom peptides.

Phosphonate analogues of the peptidomimetic N-(Furan-2-yl)carbonyl-Leu-Trp-OH were prepared with the goal of evaluating the effect of phosphonate for carboxylate replacement on binding with snake venom metalloproteinases and MMPs. N-(Furan-2-yl)carbonyl-Leu-L-Trp(P)-(OH)2 showed a 75-fold increase of the inhibiting activity against adamalysin II, a snake venom metalloproteinase structurally related to MMPs and TACE. Both the phosphonate and carboxylate peptidomimetics fit into the active site adopting a retrobinding mode and provide the structural base for a new class of metalloproteinases inhibitors.

Helicobacter pylori: optimum diagnosis and test of cure.

The fact that about 50% of the world's population is infected with Helicobacter (H.) pylori and the important role that this bacterium plays in public health have been important incentives in the search for accurate diagnostic methods. A large number of invasive and non-invasive methods have been used to diagnose H. pylori infection. Each method has its advantages and disadvantages and each practitioner should choose the best diagnostic method according to the facilities available. Non-invasive tests for the diagnosis of H. pylori infection are largely used in clinical practice and in management of patients with gastroduodenal disease. Serology is the most widespread test but its use is not advised in the post-treatment follow-up. The Urea Breath Test is a simple, safe and highly accurate method ideal for evaluating the short-term follow-up of H. pylori eradication after therapy.

2 angstrom X-ray structure of adamalysin II complexed with a peptide phosphonate inhibitor adopting a retro-binding mode.

The search of reprolysin inhibitors offers the possibility of intervention against both matrixins and ADAMs. Here we report the crystal structure of the complex between adamalysin II, a member of the reprolysin family, and a phosphonate inhibitor modeled on an endogenous venom tripeptide. The inhibitor occupies the primed region of the cleavage site adopting a retro-binding mode. The phosphonate group ligates the zinc ion in an asymmetric bidentate mode and the adjacent Trp indole system partly fills the primary specificity subsite S1'. An adamalysin-based model of tumor necrosis factor-alpha-converting enzyme (TACE) reveals a smaller S1' pocket for this enzyme.