A molecular basis for the C-domain selectivity of angiotensin-converting enzyme

Includes abstract. Includes bibliographical references (leaves 96-113)

Characterization of domain-selective inhibitor binding in angiotensin-converting enzyme using a novel derivative of lisinopril

http://dx.doi.org/10.1042/BJ2010005

Angiotensin-converting enzyme - new insights into structure, biological significance and prospects for domain-selective inhibitors.

Somatic angiotensin-converting enzyme (ACE) - well known for its role in cardiovascular pathophysiology - has an unusual, two-domain, double active-site structure. The two domains (designated N and C) are 55% identical and each contains a similar active site with overlapping but distinct substrate preferences. While both convert angiotensin I to angiotensin II in vitro, current evidence suggests the C domain site predominates in this role in vivo. The N domain site inactivates a hemoregulatory and antifibrotic peptide, AcSDKP, in vivo, although the significance of this remains unclear. However, differences in the characteristics of the two domains may result in different context-dependent activities, as is the case with other enzymes containing tandem repeats. The N domain may also have a role in modulating C domain activity, through a combination of inter-domain cooperativity and structural stabilization. Comparison of ACE with its structural homologues reveals conservation of peptidase activity and a tendency to hinge about the active-site cleft. Recent work on ACE active-site mutants containing one or more key residues replaced by their cognate residues from the other domain, synthesis of domain-selective inhibitors, and co-crystal structures of each domain with such inhibitors, has led to a better resolution of the basis for domain selectivity and should enable the design of next-generation, domain-selective inhibitors with distinct pharmacological profiles

Characterization of domain-selective inhibitor binding in angiotensin-converting enzyme using a novel derivative of lisinopril

Human ACE (angiotensin-converting enzyme) (EC 3.4.15.1) is an important drug target because of its role in the regulation of blood pressure via the renin–angiotensin–aldosterone system. Somatic ACE comprises two homologous domains, the differing substrate preferences of which present a new avenue for domainselective inhibitor design. We have co-crystallized lisW-S, a Cdomain-selective derivative of the drug lisinopril, with human testis ACE and determined a structure using X-ray crystallography to a resolution of 2.30 Å (1 Å = 0.1 nm). In this structure, lisW-S is seen to have a similar binding mode to its parent compound lisinopril, but the P2 tryptophan moiety takes a different conformation to that seen in other inhibitors having a tryptophan residue in this position. We have examined further the domain-specific interactions of this inhibitor by mutating Cdomain-specific active-site residues to their N domain equivalents, then assessing the effect of the mutation on inhibition by lisWS using a fluorescence-based assay. Kinetics analysis shows a 258-fold domain-selectivity that is largely due to the co-operative effect of C-domain-specific residues in the S2 subsite. The high affinity and selectivity of this inhibitor make it a good lead candidate for cardiovascular drug development

The palladacycle, AJ-5, exhibits anti-tumour and anti-cancer stem cell activity in breast cancer cells:

Breast cancer is the most common malignancy amongst women worldwide but despite enormous efforts to address this problem, there is still limited success with most of the current therapeutic strategies. The current study describes the anti-cancer activity of a binuclear palladacycle complex (AJ-5) in oestrogen receptor positive (MCF7) and oestrogen receptor negative (MDA-MB-231) breast cancer cells as well as human breast cancer stem cells. AJ-5 is shown to induce DNA double strand breaks leading to intrinsic and extrinsic apoptosis and autophagy cell death pathways which are mediated by the p38 MAP kinase. This study provides evidence that AJ-5 is potentially an effective compound in the treatment of breast cancer

Structure of low-order hemimorphite produced in a Zn-rich environment by cyanobacterium Leptolingbya frigida

Microbes play a fundamental role in the precipitation of silicate biominerals, thereby affecting the Si geochemical cycle. The fne mechanisms ruling biomineralization are not yet fully understood, and their microscopic structures can offer deep insight into their processes of formation, reactivity and stability. In this study, a Zn silicate biomineral, extracellularly produced by cyanobacterium Leptolingbya frigida, was investigated combining nuclear magnetic resonance (NMR), Zn K-edge X-ray absorption spectroscopy (XAS) and other complementary techniques. 29Si magic angle spinning and 29Si/1H cross polarization magic angle spinning analysis, Fourier transform infrared spectroscopy (FTIR) and XAS analysis revealed a poorly crystalline phase closely resembling hemimorphite [Zn4Si2O7(OH)2•H2O]. Zn K-edge extended X-ray absorption fne structure (EXAFS) provided further structural details, revealing that the Zn-O-Si interatomic distances were 7-8% shorter than the abiotic mineral. 13C NMR spectra analysis was conducted to investigate the composition of the Zn silicate biomineral organic matrix, and results revealed that C atoms occurred in several functional groups such as carbonyl carbons, C rings, O-aliphatic chains, N-aliphatic chains, and aliphatic chains. Under slightly alkaline conditions, bacterial cell walls exhibited fundamental control on the biomineralization process by binding Zn ions and forming Zn-O-Si bonds. In this way, L. frigida cell walls served as a reactive surface for the precipitation of this Zn sorosilicate, hindering the condensation of silicon dimers. Moreover, we found a 29Si NMR band at 85 ppm that could be attributed to a (C3H6O3)2Si complex. This complex could play a role in the control of silicon polymerization, with implications for Si biomineralization processes