PubMed · 6186697
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D J van Rhenen, W Jalink, P C Huijgens. 1983. Esterase staining in monocytes.. https://doi.org/10.1136/jcp.36.2.236
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Immobilization of membrane proteins remains a challenge compared to soluble proteins. The membrane protein-chlorophyllase was successful entrapped in tetramethoxysilane (TMOS)-based sol-gel in the presence of lipid. Activity was examined against mixing rate, incubation temperature, time, substrate, acetone, and canola oil concentration. The external mass transfer of chlorophyll is not the rate-limiting step at higher mixing rates. Stability against temperature and acetone as denaturant was enhanced. In spite of the fact that an initial reaction lag phase was observed, 20% more chlorophyll was hydrolyzed, compared to reaction with free enzyme by the end of a 12 h assay. The initial lower activity demonstrated by entrapped chlorophyllase is likely due to the diffusion resistance of chlorophyll into and within the entrapment matrix. This hypothesis was substantiated by a low diffusion coefficient on the order of 10(-14) m(2)/s obtained for chlorophyll in nanoporous sol-gel particles. Pore size distribution of nanoporous wet TMOS-based sol-gel with or without protein was determined by thermoporometry. The change in pore morphology upon doping with chlorophyllase suggests that protein acts as a template during the sol-gel process.
We have previously described the complexity of the folding of the lipolytic enzyme cutinase from F. solani pisi in guanidinium chloride. Here we extend the refolding analysis by refolding from the pH-denatured state and analyze the folding behaviour in the presence of the weaker denaturant urea and the stronger denaturant guanidinium thiocyanate. In urea there is excellent consistency between equilibrium and kinetic data, and the intermediate accumulating at low denaturant concentrations is off-pathway. However, in GdmCl, refolding rates, and consequently the stability of the native state, vary significantly depending on whether refolding takes place from the pH- or GdmCl-denatured state, possibly due to transient formation of aggregates during folding from the GdmCl-denatured state. In GdmSCN, stability is reduced by several kcal/mol with significant aggregation in the unfolding transition region. The basis for the large variation in folding behaviour may be the denaturants' differential ability to support formation of exposed hydrophobic regions and consequent changes in aggregative properties during refolding.
Zearalenone is a mycotoxin with estrogenic effects on mammals that is produced by several species of Fusarium. We found that zearalenone and its derivatives inhibit the growth of filamentous fungi on solid media at concentrations of < or =10 microg/ml. The fungitoxic effect declined in the order zearalenone > alpha-zearalenol > beta-zearalenol. The mycoparasitic fungus Gliocladium roseum produces a zearalenone-specific lactonase which catalyzes the hydrolysis of zearalenone, followed by a spontaneous decarboxylation. The growth of G. roseum was not inhibited by zearalenone, and the lactonase may protect G. roseum from the toxic effects of this mycotoxin. We inactivated zes2, the gene encoding zearalenone lactonase in G. roseum, by inserting a hygromycin resistance cassette into the coding sequence of the gene by means of Agrobacterium tumefaciens-mediated genetic transformation. The zes2 disruption mutants could not hydrolyze the lactone bond of zearalenone and were more sensitive to zearalenone. These data are consistent with a hypothesis that resorcylic acid lactones exemplified by zearalenone act to reduce growth competition by preventing competing fungi from colonizing substrates occupied by zearalenone producers and suggest that they may play a role in fungal defense against mycoparasites.