Current Enzyme Inhibition (v.7, #3)

Estrogens are known to be an important factor in the development of estrogen-sensitive diseases. Among theenzymes involved in the biosynthesis of steroid hormones, 17β-hydroxysteroid dehydrogenase type 12 (17β-HSD12) isresponsible for the reduction of estrone (E1) to estradiol (E2), this later revealed to stimulate the proliferation of estrogensensitivecells. To better understand the role of 17β-HSD12 and to better control the formation of E2 in a therapeuticperspective, we concentrated our work on synthesizing inhibitors. Knowing that a side chain at position 17β and theabsence of any functional group at position 3 of E2 are important for inhibitory activity, we generated two series of 17β-amido-3-desoxyestradiol derivatives and measured their potential as inhibitors of 17β-HSD12. Parallel liquid-phaseorganic synthesis was used to prepare library A (36 compounds), while library B (19 compounds) was generated by directcarbonylation using high density microwave irradiation. The inhibitory results have shown that compounds from library Bproduced promising inhibition of 17β-HSD12, unlike compounds from library A. Indeed, seven compounds in library Binhibited the enzyme activity (transformation of E1 to E2) by 41-57% and 69-74% at 1 and 10 βM, respectively.

Clostridium difficile DNA Polymerase IIIC: Basis for Activity of Anti- Bacterial Compounds by Andrea Torti, Andrea Lossani, Lida Savi, Federico Focher, George E. Wright, Neal C. Brown, Wei-Chu Xu (147-153).
Based on the finding that aerobic Gram-positive antibacterials that inhibit DNA polymerase IIIC (pol IIIC)were potent inhibitors of the growth of anaerobic Clostridium difficile (CD) strains, we chose to clone and express thegene for pol IIIC from this organism. The properties of the recombinant enzyme are similar to those of related pol IIICsfrom Gram-positive aerobes, e.g. B. subtilis. Inhibitors of the CD enzyme also inhibited B. subtilis pol IIIC, and werecompetitive with respect to the cognate substrate 2’-deoxyguanosine 5’-triphosphate (dGTP). Significantly, several ofthese inhibitors of the CD pol IIIC had potent activity against the growth of CD clinical isolates in culture.

The immunosuppressive oligonucleotide cyclosporine A (CsA) is extensively used in organ transplantation andautoimmune disorders. CsA as well as FK506 is a typical inhibitor of calcineurin, a serine/threonine phosphatase.Calcineurin is a potent regulator for fiber-type conversion, regeneration, and muscle hypertrophy of slow-twitch fibers.Many researchers including our group have used CsA delivered orally, intraperitoneally, or subcutaneously to modulatecalcineurin activity. In this review, we have systematically and descriptively dealt with the role of CsA in regulatingmuscle adaptations in mature mammals. Pharmacological inhibition by CsA delays the muscle regenerating process.Some limitations are observed, because treatment with CsA in vivo blocks all of the calcineurin subtypes. A strategy forcontrolling the amount of calcineurin may be effective for the treatment of muscular disorders such as Duchenne musculardystrophy (DMD), Ullrich congenital muscular dystrophy (UCMD), and limb-girdle muscular dystrophy (LGMD). Lowdoseand short-term (2-6 weeks) CsA treatment would help to elucidate the functional role of calcineurin in skeletalmuscle in vivo.

Polyphosphate Synthesis as a Target for Novel Antibiotics by Francisco P. Chavez, Carlos F. Lagos, Miguel Reyes-Parada, Nicolas Guiliani, Carlos A. Jerez (163-168).
Inorganic polyphosphate (polyP) is a biopolymer of tens or hundreds of phosphate (Pi) residues linked by highenergyphosphoanhydride bonds. PolyP has been studied mainly in prokaryotes but it is present in all species of the threedomains of life. In bacteria, polyP and its processing enzymes play important roles in cellular metabolism as well as inpathogenesis. The genomes of many bacterial species, including pathogens, encode orthologs of the main polyPsynthesizingenzyme, PPK1. This enzyme has been studied in E. coli and its metabolic inhibitors have been reported. Thehigh degree of identity between the PPK1 orthologs in some of the major pathogenic species has prompted the knockoutof their ppk1 genes to determine the dependence of virulence on polyP. Although viable, mutants lacking the ppk1 genehave reduced levels of polyP and exhibit multiple structural, functional and virulence defects.The emergence of multi-drug resistant (MDR) bacteria is the result of antibiotic overuse. Therefore, novel approaches aremuch needed to tackle them. One of these combines the reduction of bacterial virulence while simultaneously increasingsusceptibility to host defenses instead of killing the pathogen. Considering that no PPK1 orthologs have been identified inhigher-order eukaryotes, PPK1 exhibits an enormous potential as a novel target for antimicrobial drug design.In this review we focus on the current state of the art regarding polyP deficiency in pathogenic bacteria and attempts todesign inhibitors targeting enzymes responsible for the synthesis of polyP in bacteria.

Cell wall and vacuolar invertases are important regulators of plant growth; they also participate in stressresponses and modulate sink-source relationships and sugar-related signaling. Their physiological importance necessarilyrequires that their activity be tightly controlled, either by transcriptional or post-transcriptional mechanisms, to ensure anappropriate development of the plant. Knowledge regarding the way these enzymes are controlled in planta has beengradually increasing, including novel information regarding the regulatory role played by a well-known family of smallinvertase inhibitor proteins. This review complements a previous compilation dedicated to these inhibitory proteins [1]. Itwill concentrate on recent reports describing the spatiotemporal impact that invertase inhibitors appear to have in severalaspects of plant growth and development, in stress responses and in processes that have a direct influence on foodprocessing. Hitherto unknown aspects regarding their mode of action that were recently uncovered will be described, suchas co-localization and physical interaction with their target enzymes detected in planta and direct participation in (a)bioticstress responses and in the senescence process. The utilization of alternative splicing to increase the diversity andfunctionality of invertase inhibitors to facilitate the repression of the unwanted cold-induced sweetening process in potatotubers, will also be discussed, in addition to a description of the increasing body of evidence showing the biotechnologicalpotential that the manipulation of invertase inhibitor levels in plants might have on the improvement of crop productivityand fruit quality traits.

Artificial Enzymes: A Review by Vandana Sharma, Mukesh Bachwani (178-189).
Enzymes are truly outstanding biological catalysts with the ability to accelerate the rate of chemical reactionsup to 1019 times for specific substrates and reactions. New approaches based on amino acids or peptides as characteristicmolecular moieties have led to a significant expansion of the field of artificial enzymes or enzyme mimics, catalyzingvarious reactions with rate increases up to 103. A number of possibilities now exist for the construction of artificialenzymes. These are generally synthetic polymers or oligomers with enzyme-like activities, often called synzymes. Thisreview has basic information about Ideal Requirement for Artificial Enzymes Environment, Design Approach forArtificial Enzyme and their Significance for further development in this field.