Substrate specificity of a peptidyl-aminoacyl-l/d-isomerase from frog skin

In the skin of fire-bellied toads (Bombina species), an aminoacyl-l/d-isomerase activity is present which catalyses the post-translational isomerization of the l- to the d-form of the second residue of its substrate peptides. Previously, this new type of enzyme was studied in some detail and genes potentially coding for similar polypeptides were found to exist in several vertebrate species including man. Here, we present our studies to the substrate specificity of this isomerase using fluorescence-labeled variants of the natural substrate bombinin H with different amino acids at positions 1, 2 or 3. Surprisingly, this enzyme has a rather low selectivity for residues at position 2 where the change of chirality at the alpha-carbon takes place. In contrast, a hydrophobic amino acid at position 1 and a small one at position 3 of the substrate are essential. Interestingly, some peptides containing a Phe at position 3 also were substrates. Furthermore, we investigated the role of the amino-terminus for substrate recognition. In view of the rather broad specificity of the frog isomerase, we made a databank search for potential substrates of such an enzyme. Indeed, numerous peptides of amphibia and mammals were found which fulfill the requirements determined in this study. Expression of isomerases with similar characteristics in other species can therefore be expected to catalyze the formation of peptides containing d-amino acids

Identification and characterization of antibacterial compound(s) of cockroaches (Periplaneta americana)

Infectious diseases remain a significant threat to human health, contributing to more than 17 million deaths, annually. With the worsening trends of drug resistance, there is a need for newer and more powerful antimicrobial agents. We hypothesized that animals living in polluted environments are potential source of antimicrobials. Under polluted milieus, organisms such as cockroaches encounter different types of microbes, including superbugs. Such creatures survive the onslaught of superbugs and are able to ward off disease by producing antimicrobial substances. Here, we characterized antibacterial properties in extracts of various body organs of cockroaches (Periplaneta americana) and showed potent antibacterial activity in crude brain extract against methicillin-resistant Staphylococcus aureus and neuropathogenic E. coli K1. The size-exclusion spin columns revealed that the active compound(s) are less than 10 kDa in molecular mass. Using cytotoxicity assays, it was observed that pre-treatment of bacteria with lysates inhibited bacteria-mediated host cell cytotoxicity. Using spectra obtained with LC-MS on Agilent 1290 infinity liquid chromatograph, coupled with an Agilent 6460 triple quadruple mass spectrometer, tissues lysates were analyzed. Among hundreds of compounds, only a few homologous compounds were identified that contained isoquinoline group, chromene derivatives, thiazine groups, imidazoles, pyrrole containing analogs, sulfonamides, furanones, flavanones, and known to possess broad-spectrum antimicrobial properties, and possess anti-inflammatory, anti-tumour, and analgesic properties. Further identification, characterization and functional studies using individual compounds can act as a breakthrough in developing novel therapeutics against various pathogens including superbugs

Impact of cumulative exposure to high-dose oral glucocorticoids on fracture risk in Denmark: a population-based case-control study

We examined the effect of cumulative exposure to high doses of oral glucocorticoids on fracture risk. Compared to short-course users (daily dose ≥ 15 mg + cumulative < 1 g), heavy users (daily dose ≥ 15 mg + cumulative dose ≥ 1 g) had the highest risk of fracture. These patients should be monitored for fracture management strategies. PURPOSE: The effect of cumulative exposure to high daily doses of oral glucocorticoids on fracture risk remains debated. We therefore aimed to examine the hip fracture risk associated with short courses and heavy use of high-dosed oral glucocorticoids. METHODS: We conducted a population-based case-control study using the Danish National Health Service data, 1996-2011. Cases were those aged ≥ 18 years who sustained a hip (primary outcome) fracture (n = 81,342). Vertebral and forearm fractures were considered in secondary analyses. Controls (matched 1:1) were those without a fracture. Average daily dose (DD) and total cumulative dose (CD) were calculated among current oral glucocorticoid users. Among patients with a high daily dose (DD ≥ 15 mg), we identified short-course users as those with a CD < 1 g and heavy users as those with a CD ≥ 1 g. We estimated adjusted odds ratio (adj.OR) of fracture with current glucocorticoid use compared to never-use, using conditional logistic regression. RESULTS: A high DD (≥ 15 mg) and high CD (≥ 1 g) were independently associated with an increased hip fracture risk (adj.OR 2.5; 95% CI 2.2-2.9; adj.OR 1.6; 95% CI 1.5-1.8, respectively). However, the risk was substantially increased among heavy users (DD ≥ 15 mg and CD ≥ 1 g: adj.OR 2.9; 95% CI 2.5-3.4) as compared to short-course users (DD ≥ 15 mg and CD < 1 g: adj.OR 1.4; 95% CI 1.1-1.9). Associations were stronger for vertebral fractures, yet little association was identified for forearm fractures. CONCLUSION: Among patients receiving a high DD (≥ 15 mg), heavy users (≥ 1 g CD) showed the most substantial increase in hip fracture risk. Among those receiving high DD, a threshold of 1 g CD may identify heavy users that are candidates for focused fracture management services

Impact of cumulative exposure to high-dose oral glucocorticoids on fracture risk in Denmark : a population-based case-control study

We examined the effect of cumulative exposure to high doses of oral glucocorticoids on fracture risk. Compared to short-course users (daily dose ≥ 15 mg + cumulative < 1 g), heavy users (daily dose ≥ 15 mg + cumulative dose ≥ 1 g) had the highest risk of fracture. These patients should be monitored for fracture management strategies. PURPOSE: The effect of cumulative exposure to high daily doses of oral glucocorticoids on fracture risk remains debated. We therefore aimed to examine the hip fracture risk associated with short courses and heavy use of high-dosed oral glucocorticoids. METHODS: We conducted a population-based case-control study using the Danish National Health Service data, 1996-2011. Cases were those aged ≥ 18 years who sustained a hip (primary outcome) fracture (n = 81,342). Vertebral and forearm fractures were considered in secondary analyses. Controls (matched 1:1) were those without a fracture. Average daily dose (DD) and total cumulative dose (CD) were calculated among current oral glucocorticoid users. Among patients with a high daily dose (DD ≥ 15 mg), we identified short-course users as those with a CD < 1 g and heavy users as those with a CD ≥ 1 g. We estimated adjusted odds ratio (adj.OR) of fracture with current glucocorticoid use compared to never-use, using conditional logistic regression. RESULTS: A high DD (≥ 15 mg) and high CD (≥ 1 g) were independently associated with an increased hip fracture risk (adj.OR 2.5; 95% CI 2.2-2.9; adj.OR 1.6; 95% CI 1.5-1.8, respectively). However, the risk was substantially increased among heavy users (DD ≥ 15 mg and CD ≥ 1 g: adj.OR 2.9; 95% CI 2.5-3.4) as compared to short-course users (DD ≥ 15 mg and CD < 1 g: adj.OR 1.4; 95% CI 1.1-1.9). Associations were stronger for vertebral fractures, yet little association was identified for forearm fractures. CONCLUSION: Among patients receiving a high DD (≥ 15 mg), heavy users (≥ 1 g CD) showed the most substantial increase in hip fracture risk. Among those receiving high DD, a threshold of 1 g CD may identify heavy users that are candidates for focused fracture management services

Isolation, characterization and molecular cloning of new temporins from the skin of the North African ranid Pelophylax saharica

Temporins are small antimicrobial peptides isolated from North American and Eurasian ranid frogs that are particularly active against Gram-positive bacteria. To date, no temporins have been characterized from North African frog species. We isolated three novel members of the temporin family, named temporin-1Sa (FLSGIVGMLGKLF(amide)), -1Sb (FLPIVTNLLSGLL(amide)), and -1Sc (FLSHIAGFLSNLF(amide)), from the skin of the Sahara frog Pelophylax (Rana) saharica originating from Tunisia. These temporins were identified by a combined mass spectrometry/molecular cloning approach. Temporin-1Sa was found to be highly active against Gram-positive and Gram-negative bacteria, yeasts and fungi (MIC = 2-30 mu M). To our knowledge, this is the first 13-residue member of the temporin family with a net charge of +2 that shows such broad-spectrum activity with particularly high potency on the clinically relevant Gram-negative strains, Escherichia coli (MIC = 10 mu M) and Pseudomonas aeruginosa (MIC = 31 mu M). Moreover, temporin-1Sa displays significant antiparasitic activity (IC50 similar to 20 mu M) against the promastigote and amastigote stages of Leishmania infantum