Enzymological characterization of EpoA,a laccase-like phenol oxidase produced by Streptomyces griseus

Laccase is an enzyme that catalyzes the oxidation of phenolic compounds by coupling the reduction of oxygen to water. While many laccases have been identified in plant and fungal species, enzymes of prokaryotic origin are poorly known. Here we report the enzymological characterization of EpoA, a laccase-like extracytoplasmic phenol oxidase produced by Streptomyces griseus. EpoA was expressed and purified with an Escherichia coli host-vector system as a recombinant protein fused with a C-terminal histidine-tag (rEpoA). Physicochemical analyses showed that rEpoA comprises a stable homotrimer containing all three types of copper (types 1-3). Various known laccase substrates were oxidized by rEpoA, while neither syringaldazine nor guaiacol served as substrates. Among the substrates examined, rEpoA most effectively oxidized N,N-dimethyl-p-phenylenediamine sulphate with a Km value of 0.42 mM. Several metal chelators caused marked inhibition of rEpoA activity, implying the presence of a metal center essential for the oxidase activity. The pH and temperature optima of rEpoA were 6.5 and 40 degrees C, respectively. The enzyme retained 40% activity after preincubation at 70 degrees C for 60 min. EpoA-like activities were detected in cell extracts of 8/40 environmental actinomycetes strains, which suggests that similar oxidases are widely distributed among this group of bacteria.     

Characteristics and biotechnology applications of aliphatic amino acid hydroxylases belonging to the Fe(II)/α-ketoglutarate-dependent dioxygenase superfamily

The asymmetric hydroxylation of inactive carbon atoms is still an important reaction in the industrial synthesis of valuable chiral compounds such as pharmaceuticals and fine chemicals. Applications of monooxygenation enzymes, like cytochrome P450 monooxygenases, flavin-containing monooxygenases, and Fe(II)/α-ketoglutarate-dependent dioxygenases (Fe/αKG-DOs), are strongly desired as hydroxylation biocatalysts because they have great advantages in regio- and stereoselectivity of the reactions. Recently, several novel Fe/αKG-DOs have been found to catalyze the asymmetric hydroxylation of aliphatic amino acids. Depending on their amino acid sequences, these Fe/αKG-DOs catalyze different types of regioselective hydroxylations, or C3–, C4–, and C5-hydroxylation. Additionally, most also have stereoselective sulfoxidation activities. Here, we have reviewed the characterization and process development of this novel functioning group of Fe/αKG-DOs.     

High-speed electro-fusion and electro-transfection of plant protoplasts by a continuous flow electro-manipulator

A continuous flow electro-manipulator available both for mass production of fused and of transfected plant protoplasts was devised using a flow chamber with gold-coated glass panel electrodes. Up to 100 ml of protoplasts suspension were treated within 20 min at the rate of approximately 1×10⁶ protoplasts / min. The yield of diheterokaryons between tobacco mesophyll and carrot root protoplasts reached approximately 10 % of total protoplasts by flow electro-fusion. More than 95 % of tobacco and cowpea mesophyll protoplasts became infected with tobacco mosaic virus RNA by flow electro-transfection.     

The N-terminal fragment of Reelin is generated after endocytosis and released through the pathway regulated by Rab11

Reelin is a large secreted glycoprotein essential for brain formation, but its trafficking and function at the molecular level remain incompletely understood. After binding to its receptor, Reelin is internalized by endocytosis. Here we show that internalized Reelin is subject to specific proteolysis within the cell and its N-terminal fragment is re-secreted. This re-secretion is inhibited by bafilomycin A₁ or by expression of a mutant of Rab11, a regulator of the recycling pathway. As the N-terminal fragment does not bind to Reelin receptor but has homology to F-spondin, its recycling may be involved in the regulation of extracellular matrix.     

Preferential expression and immunogenicity of HIV-1 Tat fusion protein expressed in tomato plant

HIV-1 Tat plays a major role in viral replication and is essential for AIDS development making it an ideal vaccine target providing that both humoral and cellular immune responses are induced. Plant-based antigen production, due to its cheaper cost, appears ideal for vaccine production. In this study, we created a plant-optimized tat and mutant (Cys30Ala/Lys41Ala) tat (mtat) gene and ligated each into a pBI121 expression vector with a stop codon and a gusA gene positioned immediately downstream. The vector construct was bombarded into tomato leaf calli and allowed to develop. We thus generated recombinant tomato plants preferentially expressing a Tat-GUS fusion protein over a Tat-only protein. In addition, plants bombarded with either tat or mtat genes showed no phenotypic difference and produced 2–4 μg Tat-GUS fusion protein per milligram soluble plant protein. Furthermore, tomato extracts intradermally inoculated into mice were found to induce a humoral and, most importantly, cellular immunity.     

Treatment of 80 patients with Turner's syndrome with recombinant human growth hormone (YM-17798) for one year: the results of a multicentric study in Japan. Committee for the Treatment of Turner's Syndrome

A total of 80 patients with Turner's syndrome were treated with methionine-free recombinant hGH (r-hGH) for one year. Thirty-nine patients were treated with r-hGH at weekly dosage of 0.5 IU/kg and forty-one were treated with 1.0 IU/kg/w by daily sc injection. Both treatment groups showed a statistically significant growth increase during the treatment from 3.7 +/- 1.0 to 6.0 +/- 1.1 and 7.2 +/- 1.3 (mean +/- SD) cm/year, respectively. Fifty-nine percent of the patients treated with 0.5 IU/kg/w and 87.8% of the patients treated with 1.0 IU/kg/w showed a growth rate more than 2 cm greater than the pretreatment values. Plasma somatomedin C levels were elevated and no remarkable advances in bone age were observed during the treatment in both treatment groups. An antibody against to hGH was observed in 6.8% of the patients. Otherwise, there were no significant changes in physical or laboratory examinations. No glucose intolerance was observed. These results indicate that hGH treatment is useful in accelerating growth velocity in patients with Turner's syndrome.     

A dose finding study of a super long-acting luteinizing hormone-releasing hormone analog (leuprolide acetate depot, TAP-144-SR) in the treatment of central precocious puberty. The TAP-144-SR CPP Study Group.

The effect of leuprolide acetate (D-Leu6-[des-Gly10-NH2]-LH-RH ethylamide acetate) for depot suspension (TAP-144-SR), a synthetic analog of luteinizing hormone-releasing hormone, was examined in three doses in 36 patients (34 girls, 2 boys) with central precocious puberty. TAP-144-SR was injected subcutaneously every four weeks for twelve weeks, and clinical symptoms and plasma and urinary levels of various hormones were followed every four weeks. Eleven girls given 10 micrograms/kg showed a significant decrease in peak plasma LH and FSH responses to LH-RH test, but basal plasma LH and FSH did not change significantly. In 13 patients (11 girls and 2 boys) given 30 micrograms/kg and 12 girls given 90 micrograms/kg, both basal and peak LH and FSH were significantly suppressed. Urinary excretion of LH decreased significantly in all groups except in the 10 micrograms/kg group. Urinary excretion of FSH did not change significantly in the 10 and 30 micrograms/kg groups, but it decreased significantly in the 90 micrograms/kg group. In girls, plasma and urinary estradiol also fell greatly, but the difference was insignificant except in the 90 micrograms/kg group. Regression of sexual characteristics was observed in almost half of the patients at the 12th week of the treatment. Side effects were minimal. A dose of more than 30 micrograms/kg of TAP-144-SR is effective in suppressing gonadotropins and causing improvement of clinical symptoms, and appears to be useful in treating children with central precocious puberty.