Differences in metallothionein gene expression in primary cultures of rainbow trout hepatocytes and the RTH-149 cell line

Primary cultures of rainbow trout, Salmo gairdneri, hepatocytes were used to study the expression of metallothionein (MT) genes in response to steroid hormone treatment. The expression pattern was compared to that of an immortal cell line (RTH-149). MT mRNA accumulated in both cell cultures after exposure to zinc while 17 beta-oestradiol had no effect in either system. Treatment with cortisol and corticosterone resulted in a 2-fold increase of metallothionein mRNA levels in the primary cultures but had no effect in the RTH-149 cell culture. Primary cultures that were exposed to zinc or cortisol showed a high temporal correlation (r = 0.974) between MT mRNA and MT protein levels. The basal level expression was 3-4-fold higher in primary cultures than in RTH-149 cells. The present study demonstrates the inducibility of rainbow trout MT genes in response to glucocorticoids. It further indicates that primary cultures are to be preferred to immortal cell lines when investigating the inducibility of MT mRNA.     

Enzymatic catalysis in microemulsions: enzyme reuse and product recovery

A technique for enzyme reuse and product recovery from enzymatic catalysis in microemulsions is demonstrated. The enzymatic reaction is performed in a homogeneous isotropic microemulsion; AOT (sodium bis-(2-ethyl- hexyl)sulfosuccinate)/isooctane/buffer or C(12)E(5)(penta ethylene glycol dodecyl ether)/heptane/buffer. By small temperature changes the systems are shifted to two phase regions, where an oil-rich phase, containing the product, coexists with a water-rich phase containing surfactant and enzyme. The oil-rich phase may be replaced by an oil solution containing new substrate. Thus, the reaction may be continued and the enzyme reused. This procedure was repeated nine times in the present study. Data on phase behavior in presence and in absence of protein, partitioning of the components and a radioactive-labelled protein between the phases, and the repeated use of horse liver alcohol dehydrogenase (HLADH) in the microemulsions are presented.     

Analysis of rpsD mutations in Escherichia coli

Summary A certain proportion of protein S7 exists in an altered form in E. coli rpsD (S4) mutants. Depending on the type of S4 mutation involved, two different forms of the altered S7 can be distinguished. The unusual form is longer than normal S7 by about 500 daltons due to extra material at the carboxyl end of the protein. It is suggested that a mutationally altered S4 might lower the efficiency of termination during translation of the messenger for S7. This results in an increased frequency of translational read-through, which gives the observed longer forms of S7. Data are interpreted to mean that one class of S4 mutants might suppress UGA and UAG whereas another class only suppresses UGA.     

Purification and properties of four species of lysyl oxidase from bovine aorta

Lysyl oxidase of bovine aorta was resolved into four enzymically active species by elution from DEAE-cellulose with a salt gradient in 6m-urea, consistent with purification results obtained with enzyme of other tissues [Stassen (1976) Biochim. Biophys. Acta438, 49-60]. In the present study, each of the four peaks of activity was purified to apparent homogeneity by subsequent chromatography on gel-filtration media in 6m-urea. Each enzyme is eluted as a species with mol.wt. approx. 30000 under these conditions, although lysyl oxidase polymerizes to a series of multimers with molecular weights ranging up to 1000000 in the absence of urea. The apparent subunit molecular weight of each enzyme species determined by electrophoresis in sodium dodecyl sulphate and 8m-urea is approx. 32000-33000. The amino acid compositions of the purified forms of lysyl oxidase are similar to each other, although sufficient differences exist to conclude that each is a unique molecular species. Incorporation of alpha-toluenesulphonyl fluoride into the purification scheme does not alter the resolution of enzyme into four species, suggesting that proteolysis during isolation is not the basis of the heterogeneity. The similar sensitivities of each form of enzyme to chelating agents and to semicarbazide and isoniazid indicate that each requires the participation of a metal ion, presumably Cu(2+), and of a carbonyl compound for enzyme function. The present study describes a method for the purification of multiple species of lysyl oxidase and reveals that significant chemical differences exist between the different enzyme forms.     

Immobilization of enzymes based on hydrophobic interaction. III. Adsorbent substituent density and its impact on the immobilization of β-amylase

Hexyl-groups have been introduced into crosslinked Sepharose 6B, yielding gels with degrees of substitution which range from 0.02 to 0.70 mol hexyl-side chain per mole galactose residue. The gels were exposed to β-amylase in solution, and the resulting adsorbates indicated a monotonic increase in adsorption capacity with an increasing hexyl-content. Adsorbate activity, by contrast, displayed a maximum for a carrier gel with a hexyl–galactose ratio of 0.51. Adsorbates based on gels with different hexyl-content were used in column reactors for continuous maltose production from a soluble starch substrate.