Development and Optimization of a High-Throughput Screening Assay for Rapid Evaluation of Lipstatin Production by Streptomyces Strains

Microtiter Plate Cultivation Systems Enable Chemically Diverse Metabolic Footprints During Bacterial Natural Product Discovery

Rediscovery of known structures is a frequent problem in screening for bioactive bacterial natural products (NPs). Highly parallelized microtiter plate cultivation systems (MPCS) can improve the chance to discover novel NPs by testing a multitude of cultivation conditions simultaneously. An in-depth analysis and comparison of cultivation systems for NP discovery, however, has not been carried out so far. We compared the growth and metabolic footprint of four distinct bacterial species in three MPCS, shake flasks, and stirred tank bioreactors (STR). While the big majority of the cultivation systems provided good growth, we found a considerable divergence in secondary metabolite (SM) formation. The SM space was approximated by the appearance of unique mass features (MFs) in the supernatant extracts throughout the cultivation period. Molecular network analysis was applied to visualize the changes from detected MFs at the molecular level. The cultivation systems had a minor impact on the unicellular growing Bacillus amyloliquefaciens. This impact was more pronounced for the tested filamentous bacteria, resulting in a diversified metabolic footprint. The maximal overlap of 31% of produced MFs indicates a lack of comparability between the cultivation systems, resulting in different entries of growth phases and the formation of associated SMs. The detected SMs and its derivatives exhibited structural modification depending on the cultivation system. A comparison of Streptomyces griseochromogenes NP profile revealed that MPCS yielded less divergent SM formation than shake flasks. Our comprehensive assessment is the first to demonstrate the impact of cultivation systems on the bacterial metabolic footprint, confirming that MPCS provide a robust platform for the parallelization of bacterial cultivations for the discovery of bacterial NPs and accessing the chemical NP space more broadly.

Discovery of lignans and curcuminoids as the effective inhibitors of pancreatic lipase: structure-activity relationship and inhibitory mechanism

Pancreatic lipase (PL) is the main enzyme in the digestive system that breaks down triglyceride and promotes its absorption. In this paper, we found that lignans 2, 3 and 21, curcuminoids 24-26 exhibited significant inhibitory potential against PL. The structure-activity relationship (SAR) indicated that benzo-1, 3-dioxole group in the construction of lignans is essential to inhibitory effects against PL, while double bonds at C-7/C-2 position and 4-hydroxyphenyl moiety in the structure of curcuminoids are beneficial for PL inhibition. The kinetic studies and molecular docking were also conducted, the results showed that the three curcuminoids with the strongest inhibition effect above were all mixed inhibitors of PL. Furthermore, curcuminoids 24-26 displayed a preferential selectivity towards, in contrast to other serine hydrolases. The above results indicate that lignans and curcuminoids are natural functional components for PL inhibition, providing new ideas for finding and developing novel lead compounds for the treatment of obesity.

Methodologies for Assessing Pancreatic Lipase Catalytic Activity: A Review

Obesity is a disease of epidemic proportions with a concerning increasing trend. Regarded as one of the main sources of energy, lipids can also represent a big part of an unnecessary intake of calories and be, therefore, directly related to the problem of obesity. Pancreatic lipase is an enzyme that is essential in the absorption and digestion of dietary fats and has been explored as an alternative for the reduction of fat absorption and consequent weigh loss. Literature describes a great variability of methodologies and experimental conditions used in research to evaluate the in vitro inhibitory activity of compounds against pancreatic lipase. However, in an attempt to choose the best approach, it is necessary to know all the reaction conditions and understand how these can affect the enzymatic assay. The objective of this review is to understand and summarize the methodologies and respective experimental conditions that are mainly used to evaluate pancreatic lipase catalytic activity. 156 studies were included in this work and a detailed description of the most commonly used UV/Vis spectrophotometric and fluorimetric instrumental techniques are presented, including a discussion regarding the differences found in the parameters used in both techniques, namely enzyme, substrate, buffer solutions, kinetics conditions, temperature and pH. This works shows that both UV/Vis spectrophotometry and fluorimetry are useful instrumental techniques for the evaluation of pancreatic lipase catalytic activity, presenting several advantages and limitations, which make the choice of parameters and experimental conditions a crucial decision to obtain the most reliable results.

Inhibition of Phospholipase by Orlistat as an Alternate Therapy to Combat Opportunistic Mycosis Caused by C. albicans

Candida albicans is one of the most important etiological agents causing an opportunistic mycosis, candidiasis. In the past, it was perceived to be associated with immunocompromised patients only. However, it has now been reported with several clinical complications with varying severity. Additionally, increasing incidences of multiple drug resistance associated with the infections have complicated its treatment as well. Therefore, an investigation of alternate therapy, for instance, inhibition of the virulence factors is desperately needed. In the present study, a multidrug-resistant Candida albicans SDL-4 was screened for secretion of the virulence factors: aspartyl proteases and phospholipases. The pathogen secreted phospholipases potentially compared to aspartyl proteases. Therefore, C. albicans SDL-4 phospholipase was purified to homogeneity, characterized, and its inhibition was studied subsequently. It catalysed the substrate, p-nitrophenyl palmitate, optimally in 0.1 M acetate buffer, pH 5, at 37 °C. In the present study, we also aimed to re-purpose orlistat, which is a commercially available anti-obesity drug. Orlistat, at the concentration of 360 μg/ml, could diminish the activity and stability of the candidal virulence factor. Its half-life was reduced in the presence of orlistat at 37 °C. As well, increase in K_m and unaltered V_max indicated that orlistat inhibited phospholipase competitively. The inhibition kinetics was supported by measuring alterations in the secondary structure of the candidal phospholipase upon treatment with orlistat by the circular dichroism spectroscopy and K2D3. Moreover, validation of the study at clinical level may establish orlistat as a supportive treatment to reduce invasiveness and related medical intricacies during candidiasis.

Weak Microbial Metabolites: a Treasure Trove for Using Biomimicry to Discover and Optimize Drugs

For decades, traditional drug discovery has used natural product and synthetic chemistry approaches to generate libraries of compounds, with some ending as promising drug candidates. A complementary approach has been to adopt the concept of biomimicry of natural products and metabolites so as to improve multiple drug-like features of the parent molecule. In this effort, promiscuous and weak interactions between ligands and receptors are often ignored in a drug discovery process. In this Emerging Concepts article, we highlight microbial metabolite mimicry, whereby parent metabolites have weak interactions with their receptors that then have led to discrete examples of more potent and effective drug-like molecules. We show specific examples of parent-metabolite mimics with potent effects in vitro and in vivo. Furthermore, we show examples of emerging microbial ligand-receptor interactions and provide a context in which these ligands could be improved as potential drugs. A balanced conceptual advance is provided in which we also acknowledge potential pitfalls-hyperstimulation of finely balanced receptor-ligand interactions could also be detrimental. However, with balance, we provide examples of where this emerging concept needs to be tested. SIGNIFICANCE STATEMENT: Microbial metabolite mimicry is a novel way to expand on the chemical repertoire of future drugs. The emerging concept is now explained using specific examples of the discovery of therapeutic leads from microbial metabolites.

Bacillus subtilis Lipase A—Lipase or Esterase?

The question of how to distinguish between lipases and esterases is about as old as the definition of the subclassification is. Many different criteria have been proposed to this end, all indicative but not decisive. Here, the activity of lipases in dry organic solvents as a criterion is probed on a minimal α/β hydrolase fold enzyme, the Bacillus subtilis lipase A (BSLA), and compared to Candida antarctica lipase B (CALB), a proven lipase. Both hydrolases show activity in dry solvents and this proves BSLA to be a lipase. Overall, this demonstrates the value of this additional parameter to distinguish between lipases and esterases. Lipases tend to be active in dry organic solvents, while esterases are not active under these circumstances.