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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1978 M68 / Master of Science

BACKGROUND:The major Dengue virus vector Aedes aegypti requires nutrients obtained from blood meal proteins to complete the gonotrophic cycle. Although bioinformatic analyses of Ae. aegypti midgut serine proteases have provided evolutionary insights, very little is known about the biochemical activity of these digestive enzymes.RESULTS:We used peptide specific antibodies to show that midgut serine proteases are expressed as zymogen precursors, which are cleaved to the mature form after blood feeding. Since midgut protein levels are insufficient to purify active proteases directly from blood fed mosquitoes, we engineered recombinant proteins encoding a heterologous enterokinase cleavage site to permit generation of the bona fide mature form of four midgut serine proteases (AaET, AaLT, AaSPVI, AaSPVII) for enzyme kinetic analysis. Cleavage of the chromogenic trypsin substrate BApNA showed that AaET has a catalytic efficiency (kcat/KM) that is ~30 times higher than bovine trypsin, and ~2-3 times higher than AaSPVI and AaSPVII, however, AaLT does not cleave BApNA. To measure the enzyme activities of the mosquito midgut proteases using natural substrates, we developed a quantitative cleavage assay based on cleavage of albumin and hemoglobin proteins. These studies revealed that the recombinant AaLT enzyme was indeed catalytically active, and cleaved albumin and hemoglobin with equivalent efficiency to that of AaET, AaSPVI, and AaSPVII. Structural modeling of the AaLT and AaSPVI mature forms indicated that AaLT is most similar to serine collagenases, whereas AaSPVI appears to be a classic trypsin.CONCLUSIONS:These data show that in vitro activation of recombinant serine proteases containing a heterologous enterokinase cleavage site can be used to investigate enzyme kinetics and substrate cleavage properties of biologically important mosquito proteases.

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Gelatin was extracted from shark and salmon skins by an enzyme aided process. A three factor, two level central composite rotatable design was used to optimize the process. The factors were namely, enzyme: dry fish skin weight ratio, incubation time, and temperature. The data were analyzed by response surface methodology to determine the optimum conditions for the deproteinization, demineralization and extraction process variables. / Optimum conditions for deproteinization of shark skin by trypsin was about 25°C for 3h, and an E/S ratio of 0.08% (w/w). That for salmon was optimum at 25°C for 1 h with an E/S ratio of 1:1000. The ash content of the shark skins was reduced to over 80% at optimum demineralization conditions of 0.7M citric acid at 25°C for 3h. / Demineralised salmon skins treated with pepsin at an E/S ratio of 0.02% (w/w) for 1h at 25°C resulted in maximum gelatin yield ranging from 7--8%. For shark, the maximum yield was between 18--20% at an E/S ratio of 0.02% (w/w) for 3h at 25°C. The chemical and enzyme treatments had an effect on the viscosity, bloom value and molecular weight for both salmon and shark gelatins.

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Many proteins with special properties have been identified in aquatic organisms. Due to their peculiarity, some of these biomolecules could be used advantageously for some industrial and health care applications. However, the preparation of these biochemicals from its original source is highly impractical and generally unfeasible for commercial purposes. Nevertheless, the advances in DNA manipulation open the possibility of producing the recombinant proteins in different organisms to allow a viable production and extraction on a commercial scale. Among such particular proteins, the cunner-fish trypsin (CFT) is an enzyme with a high potential for exploitation by the food processing industry. The CFT is a cold adapted protease that has a proven ability to inactivate undesirable endogenous enzymes during the processing of some foodstuffs. Thus, the CFT gene was characterized and cloned in E. coli and Pichia pastoris for over-expression. A cDNA library from pancreatic mRNA was screened using a salmon trypsin cDNA probe. Positive clones harboring a cDNA insert of the predicted size were sequenced and a full-length cDNA was obtained that contained an ORF encoding the zymogen and a signal peptide. Multiple alignment of the gene sequence showed 85 to 90 per cent identities with other fish trypsins and the deduced amino acid sequence for the mature enzyme exhibited the entire characteristic features observed in trypsins. E. coli expressed the recombinant CFT (rCFT) at levels higher than 20% in the form of insoluble aggregates, while P. pastoris showed expression levels below 1%. Despite the low expression, the yeast rCFT appeared to be correctly folded and could be partially purified by immobilized nickel affinity chromatography. Trypsin-specific activity was confirmed in the purified rCFT after digestion with bovine enterokinase.

Coacervation is a mild process for developing protein NPs. Bovine serum albumin (BSA) NPs formed via this technique were stabilized using poly-L-Lysine (PLL); short interfering ribonucleic acid (siRNA) was used as a model drug for encapsulation. Specific and non-specific degradation of these coated and uncoated BSA NPs were carried using matrix metalloproteinase-2 (MMP-2) and trypsin, respectively. The particles were characterized with atomic force microscopy, zeta-potential, and photon correlation spectroscopy measurements. There was a significant increase in the zeta potential of BSA NPs upon coating. Trypsin digested the uncoated and coated BSA NPs and resulted in higher BSA release from the particles. However, MMP-2 treatment did not result in higher release of BSA from coated NPs despite the cleavability of coated polymer by MMP-2. This study described a method for obtaining BSA NPs in a controllable size range. Such particles showed degradability in the presence of trypsin and could be promising for targeted drug delivery applications. / Chemical Engineering