Optimal spatial allocation of enzymes as an investment problem

Given a limited number of molecular components, cells face various allocation problems demanding decisions on how to distribute their resources. For instance, cells decide which enzymes to produce at what quantity, but also where to position them. Here we focus on the spatial allocation problem of how to distribute enzymes such as to maximize the total reaction flux produced by them in a system with given geometry and boundary conditions. So far, such distributions have been studied by computational optimization, but a deeper theoretical understanding was lacking. We derive an optimal allocation principle, which demands that the available enzymes are distributed such that the marginal flux returns at each occupied position are equal. This ‘homogeneous marginal returns criterion’ (HMR criterion) corresponds to a portfolio optimization criterion in a scenario where each investment globally feeds back onto all payoffs. The HMR criterion allows us to analytically understand and characterize a localization-delocalization transition in the optimal enzyme distribution that was previously observed numerically. In particular, our analysis reveals the generality of the transition, and produces a practical test for the optimality of enzyme localization by comparing the reaction flux to the influx of substrate. Based on these results, we devise an additive construction algorithm, which builds up optimal enzyme arrangements systematically rather than by trial and error. Taken together, our results reveal a common principle in allocation problems from biology and economics, which can also serve as a design principle for synthetic biomolecular systems.

Histochemical Distribution of Acetylcholinesterase in the Forebrain Nuclei of an Indian Non Catfish Channa punctatus

Background: Acetylcholinesterase (AChE) is an enzyme belonging to hydrolase group which splits the acetylcholine in to choline and acetate. It is supposed to be a marker of cholinergic and cholinoceptive neurons. Acetylcholinesterase histochemisry has been done in a number of vertebrates but it is still obscure and scattered in fishes, particularly in Indian fishes. Methods: In the present study a modified histochemical technique has been employed to histochemically map the acetylcholinesterase containing neurons in the telencephalic and diencephalic nuclei of C. punctatus described by Hedreen, et al (1985).Result: Acetylchoinesterase is differentially expressed in the various prosencephalic centres and nuclei of the brain, thus its staining clearly demarcates these centres and nuclei based on varying enzyme intensity. Among the pallial nuclei of the forebrain, medial and dorsolateral nuclei showed intense enzyme activity while ventral dorsolateral nucleus and central nucleus showed moderate reaction. In contrast, most of the subpallial nuclei of the forebrain showed high intensity. Diencephalic nuclei of the forebrain exhibited mosaic pattern of enzyme distribution.

Semi-Solid Pharmaceutical Formulations for the Delivery of Papain Nanoparticles

Papain is a therapeutic enzyme with restricted applications due to associated allergenic reactions. Papain nanoparticles have shown to be safe for biomedical use, although a method for proper drug loading and release remains to be developed. Thus, the objective of this work was to develop and assess the stability of papain nanoparticles in a prototype semi-solid formulation suitable for dermatological or topical administrations. Papain nanoparticles of 7.0 ± 0.1 nm were synthesized and loaded into carboxymethylcellulose- and poly(vinyl alcohol)-based gels. The formulations were then assayed for preliminary stability, enzyme activity, cytotoxicity studies, and characterized according to their microstructures and protein distribution. The formulations were suitable for papain nanoparticle loading and provided a stable environment for the nanoparticles. The enzyme distribution along the gel matrix was homogeneous for all the formulations, and the proteolytic activity was preserved after the gel preparation. Both gels presented a slow release of the papain nanoparticles for four days. Cell viability assays revealed no potential cytotoxicity, and the presence of the nanoparticles did not alter the microstructure of the gel. The developed systems presented a potential for biomedical applications, either as drug delivery systems for papain nanoparticles and/or its complexes.

Organosolv lignin properties and their effects on enzymatic hydrolysis

Lignin plays a crucial role in enzymatic hydrolysis of lignocellulosic biomass. To evaluate the correlation between lignin properties and its effects on enzymatic hydrolysis, five organosolv lignins (OLs) were isolated from woody biomass, and their physico-chemical properties and structural features were characterized. The effects of OL addition on enzymatic hydrolysis of microcrystalline cellulose (pure cellulose) were assessed first, which showed their disparate effects. The addition of three OLs increased the 72 h hydrolysis yield by 7.4% to 10.1%, while the addition of other two OLs reduced the 72 h hydrolysis yield by 3.2% to 20.4%. A strong correlation between the enzyme distribution coefficient on lignins and the 72 h hydrolysis yields indicated that the enzyme-lignin interaction played a significant role in determining the lignin effects. More importantly, a correlation between lignin properties (hydrophobicity, zeta potential, and particle size) and the enzyme distribution coefficient was established. Identifying the key lignin properties will give insights to reduce the lignin inhibition by altering the lignin properties, thereby promoting enzymatic hydrolysis of lignocellulose.

Cross-diffusion induced patterns for a single-step enzymatic reaction

Several different enzymes display an apparent diffusion coefficient that increases with the concentration of their substrate. Moreover, their motion becomes directed in substrate gradients. Currently, there are several competing models for these transport dynamics. Here, we use mathematical modeling and numerical simulations to analyze whether the enzymatic reactions can generate a significant feedback from enzyme transport onto the substrate profile. We find that this feedback can generate spontaneous spatial patterns in the enzyme distribution, with just a single-step catalytic reaction. However, patterns are formed only for a subclass of transport models. For such models, nonspecific repulsive interactions between the enzyme and the substrate, or attractive interactions between the enzyme and the product, cause the enzyme to accumulate in regions of low substrate concentration. Reactions then amplify local substrate and product fluctuations, causing enzymes to further accumulate where substrate is low. Experimental analysis of this pattern formation process could discriminate between different transport models.

Metalloproteinases secretion from cultured cells: Differentiation by detergents

Aim: Matrix metalloproteinases, particularly MMP-2 and MMP-9, are the active factors influencing the structure and properties of the extracellular matrix. This effect is enhanced in metastasis. Hence, it is necessary to enrich the knowledge of the relation between the accumulation and distribution of the enzymes in cells and the intensity of their secretion. Material/Methods: The study was conducted on three cell lines of dermal origin: normal line of human dermal fibroblasts (NHDF) and two melanoma lines (BM and B16F10). The results were obtained with substrate zymography, immunofluorescence microscopy and detergent-complemented fluorimetric assay. Results: All the studied cell lines revealed relatively rich content of MMP-2 (latent and active) with random intracellular localization. Nevertheless, the enzyme secretion was differentiated in various types of cells. The most intensive proMMP-2 secretion was obtained for NHDF, relatively lower for BM, and the lowest for B16F10 line. Zymographic detection of the active form of MMP-2 was restricted to NHDF and BM cell lines. On the other hand, differentiating usage of detergents Brij 35P and Triton X-100 evidenced an active fraction of MMP-2 present in cells of all studied lines. Triton X-100-generated lysis of cells of high MMP-2 secretion (NHDF, BM) revealed the presence of intracellular inhibitors. Conclusions: From the obtained results it can be concluded that the active form of MMP-2 is localized pericellularly in studied cells, being a minor fraction of a total amount of cellular MMP-2. The rest of the enzyme content is located deeper in cell cytoplasm in a latent form. The activity of the pericellular fraction of the enzyme can be measured with detergent-complemented fluorimetric assay, constituting a potentially useful tool for evaluating the enzyme distribution.

Impact of substrate diffusion and enzyme distribution in 3D-porous electrodes: a combined electrochemical and modelling study of a thermostable H2/O2enzymatic fuel cell

High massic catalytic currents and long-term stability are reached in a thermostable H2/O2enzymatic fuel cell.