The kinetics of the adsorption of human gastric lipase (HGL) and human pancreatic lipase (HPL) were studied by recording the changes in the surface pressure with time in the absence and presence of an egg phosphatidylcholine (PC) monomolecular film spread at the air/water interface. In the presence of PC film, the tensioactivtty of HGL increased considerably compared with its behaviour at the air/water interface, whereas HPL exhibited a comparable degree of tensioactivity whether or not a phospholipid monolayer was present at the interface. This difference in surface behaviour is consistent with the higher penetration capacity attributed to HGL. Procolipase considerably increased both the initial adsorption rate and the final surface pressure reached by HPL compared with its adsorption without colipase.
The kinetics of the hydrolysis of 1,2-didecanoyl-sn-glycerol (dicaprin) monolayers by HGL and HPL were measured using a “zero-order” trough. The large differences between the calculated characteristic adsorption times and the measured lag times indicate that the partition of the lipase molecules between the subsurface and the interface was probably limited by an energy barrier. The amplitude of this energy barrier can be partly attributed to the drastic conformational change in the enzyme, associated with the interfacial activation.
The area per dicaprin molecule (56 Å2) corresponding to the maximal activity of HPL was compared with the dimension of the hydrophobic cleft surrounding the serine (Ser 152) of the catalytic triad of HPL, as recently demonstrated by H. Van Tilbeurgh and co-workers (Nature, 359 (1992) 159; 362 (1993) 814) in their studies on the “open” and “closed” forms of the respective three-dimensional crystalline structures. The catalytic triad was not accessible to a sphere 8.4 Å in diameter, mimicking the van der Waals envelope of the dicaprin molecule, due to the steric hindrance of the side chains of aromatic and cyclic residues F 215, F 77, Y 114 and H 263. It can be concluded that the substrate molecule must also undergo some conformational changes at the contact of the enzyme to be accommodated in the active site. 相似文献
The primary objective of this work is to evaluate the potential of silica gel encapsulated pancreatic islets of Langerhans,
or islet tissue, as a means by which insulin secretory capacity might be restored to individuals with insulin dependent, type
1, diabetes mellitus. The encapsulation material under investigation is comprised of sol-gel derived silica ceramic that hardens
under conditions of pH, salinity, and temperature that are not harmful to living cells and organisms. Preliminary efficacy
has been demonstrated by measurement of insulin secretory response of silica gel encapsulated pancreatic isletsin vitro and blood sugar levels of nonobese diabetic micein vivo. 相似文献
A series of twelve novel hybrids of cinnamic acid and thiocarbohydrazones were designed, synthesized in high yield using a simple coupling strategy via acid chlorides, and evaluated for their impact against Mycobacterium tuberculosis (Mtb) and cancer cells survival. Among them, compound 3 demonstrated strong anti-Mtb activity by reducing bacilli survival for>90 % in all three treated Mtb isolates, whereas isoniazid and rifampicin did not. Moreover, compound 3 didn’t affect vitality of HepG-2 cells, implying on advantageous hepatotoxicity profile compared to current therapeutic options for tuberculosis. Compounds 2a and 3b displayed as strong inducers of apoptosis in A549 cells, both activating intrinsic caspase pathway and cell cycle arrest at the G0/G1 phase. Subsequent analyses disclosed differences in their activities, where 3b has ability to induce production of mitochondrial superoxide anions, while 2a significantly inhibited cellular mobility. More importantly, 3b considerably affected viability of HepG-2 and HaCaT cells, whereas 2a had moderate impact only on the later. Molecular modeling studies indicated high permeability and good absorption through the human intestine, and moderate aqueous solubility with poor blood–brain barrier permeability. In summary, our results reveal that novel compounds 3 and 2a represent promising agents for tuberculosis and cancer treatment, respectively, indicating that further investigation needs to be performed to clarify the mechanisms of their anti-Mtb and anticancer activity. 相似文献
Summary A combination of molecular modeling and molecular dynamics (MD) is used to determine a theoretical structure for neuropeptide Y (NPY). Starting with the X-ray structure for avian pancreatic polypeptide (APP), the substituted amino acids were mutated, the side chains oriented to local potential energy minima, and the entire structure minimized and subjected to an MD simulation. Comparison of the resulting NPY structure with APP X-ray and MD results showed secondary structural elements to be maintained and RMS fluctuations to be similar, although differences in both were observed. The approach presented offers a means to study the structure-function relationships of NPY and other similar polypeptides when combined with pharmacological measurements.Abbreviations NPY
Neuropeptide Y
- APP
Avian pancreatic polypeptide
- ABNR
Adopted-basis Newton Raphson
- MD
Molecular dynamics 相似文献
Poly(ether esters) are rapidly synthesized in moderate yield employing the interfacial polycondensation reaction system from the reaction of alpha-cyano-4-hydroxycinnamic acid and Group IVB metallocenes. The products are high polymers. Infrared spectroscopy shows the formation of new bands derived from the M-O and M-O(CO) linkages. It also shows that the products exist as alternating M-O and M-O(CO) linkages. The products show outstanding inhibition of a variety of cancer cell lines including two pancreatic cancer cell lines. EC50 values for the polymers are in the nanogram/mL range. The ability to inhibit the cancer cell lines is generally Hf>Zr>Ti. Thus, future synthesis and testing might consider using compounds containing hafnocene and zirconocene in addition to the titanocene moiety. 相似文献
Cetilistat (CET) is a pancreatic lipase inhibitor approved for management of obesity after the serious adverse effects exhibited by its analogue orlistat. Exhaustive literature review reveals lack of comprehensive reports on its biotransformation. With a view to study the same, the present study reports the identification and characterization of metabolites of CET in rats using UPLC–MS/MS. As the small intestine is the site of action for CET, it is important that the role of microbial flora in the metabolism of CET be explored. To achieve this, the metabolic profile of CET was compared between normal and pseudo-germ-free rats. The study involved the administration of a drug suspension to male Sprague–Dawley pseudo-germ-free and normal untreated rats followed by collection of urine, feces, and blood at specific intervals. Sample preparation was performed using liquid–liquid extraction and concentration of samples followed by analysis using LC–MS/MS. Finally, an in silico study was performed on the drug and metabolites to predict their toxicological properties using ADMET PredictorTM software. Four metabolites of CET were observed in in vivo matrices. As expected, significant changes were observed both qualitatively and quantitatively, implying that formation of metabolites was both CYP enzymes and gut microflora mediated. 相似文献
Abstract A self-deconvolution and fitting procedure is presented that allows the determination of pressure-induced changes in the secondary structure of proteins starting from the infrared spectrum. The method takes into account the elastic as well as the possible conformational shift of the spectral bands. Applications are presented on pressure-induced changes in bovine pancreatic trypsin inhibitor and in gramicidin incorporated into lipid bilayers. 相似文献
Lung adenocarcinoma (LUAD) is the second most common cancer, affecting both men and women. Fibrosis is a hallmark of LUAD occurring throughout progression with excess production of extracellular matrix (ECM) components that lead to metastatic cell processes. Understanding the ECM cues that drive LUAD progression has been limited due to a lack of tools that can access and report on ECM components within the complex tumor microenvironment. Here, we test whether low‐grade LUAD can be distinguished from normal lung tissue using a novel ECM imaging mass spectrometry (ECM IMS) approach. ECM IMS analysis of a tissue microarray with 20 low‐grade LUAD tissues and 20 normal lung samples from 10 patients revealed 25 peptides that could discriminate between normal and low‐grade LUAD using area under the receiver‐operating curve (AUC) ≥0.7, P value ≤.001. Principal component analysis demonstrated that 62.4% of the variance could be explained by sample origin from normal or low‐grade tumor tissue. Additional work performed on a wedge resection with moderately differentiated LUAD demonstrated that the ECM IMS analytical approach could distinguish LUAD spectral features from spectral features of normal adjacent lung tissue. Conventional liquid chromatography with tandem mass spectrometry (LC‐MS/MS) proteomics demonstrated that specific sites of hydroxylation of proline (HYP) were a main collagen post translational modification that was readily detected in LUAD. A distinct peptide from collagen 3A1 modified by HYP was increased 3.5 fold in low‐grade LUAD compared with normal lung tissue (AUC 0.914, P value <.001). This suggests that regulation of collagen proline hydroxylation could be an important process during early LUAD fibrotic deposition. ECM IMS is a useful tool that may be used to define fibrotic deposition in low‐grade LUAD. 相似文献