Over-expression system for secretory phospholipase D by Streptomyces lividans

The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle vector-pUC702-for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10(4) U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5x10(4) U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10(3) U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.

Improvement in enzyme activity and stability by addition of low molecular weight polyethylene glycol to sodium bis(2-ethyl-L-hexyl)sulfosuccinate/isooctane reverse micellar system

The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-l-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse micellar system, the phase diagram of AOT/ PEG 400/water/isooctane system was studied. The influences of relevant parameters on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable, retaining >75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics parameter maximum velocity (Vmax) exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by the addition of PEG 400.

Identification of novel membrane-bound phospholipase D from Streptoverticillium cinnamoneum, possessing only hydrolytic activity

A membrane-bound phospholipase D (PLD) has been identified and isolated in a soluble form from an actinomycete, Streptoverticillium cinnamoneum. The enzyme has a monomeric structure with a molecular size of about 37 kDa, being the smallest among the enzymes so far reported. The enzyme catalyzes the hydrolysis of phosphatidylethanolamine and phosphatidylserine as preferred substrates, but not the transphosphatidylation reaction of their phospholipid groups to ethanol. Together with the absence of immunochemical cross-reactivity, these enzymatic properties demonstrate that the membrane-bound enzyme is distinct from the extracellular enzyme recently characterized and cloned from the same bacterial strain [C. Ogino et al., J. Biochem. 125 (1999) 263-269] and is therefore regarded as a novel prokaryotic PLD.

The 5-HT(1A) receptor agonist, 8-OH-DPAT, attenuates stress-induced anorexia in conjunction with the suppression of hypothalamic serotonin release in rats

The effect of the selective 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) on stress-induced anorexia and serotonin (5-HT) release in the rat hypothalamus was studied with brain microdialysis. Subcutaneous injection of 8-OH-DPAT (1 mg/kg) significantly attenuated the immobilization-induced anorexia for 3 h, but had no effect during the following 9 h. Injection of 8-OH-DPAT itself had no effect on basal release of 5-HT, while it significantly blocked the immobilization-induced 5-HT release in the lateral hypothalamus. The results suggest that 8-OH-DPAT attenuated the stress-induced anorexia through the activation of 5-HT(1A) autoreceptors in dorsal raphe nucleus.

Lennox-Gastaut syndrome after a further attenuated live measles vaccination

We reported a 2-year-old boy with Lennox-Gastaut syndrome, of which the cause could be an adverse effect of further attenuated live (FL) measles vaccine. The pre- and peri-natal histories of the patient were uneventful, except that he was one of monozygotic twins. He had developed normally until 24 months of life, when tonic seizures began on postvaccination day 14 without a preceding episode of continuous fever or any neurologic symptoms. The tonic seizures and atypical absence have been intractable as to various antiepileptic drugs, while his twin brother has experienced no epileptic seizures.

Purification, characterization, and sequence determination of phospholipase D secreted by Streptoverticillium cinnamoneum

Phospholipase D (PLD), secreted into the culture medium of an actinomycete, Streptoverticillium cinnamoneum, has been purified to homogeneity and characterized. The Stv. cinnamoneum PLD efficiently catalyzes both the hydrolysis and transphosphatidylation of various phospholipids, including phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS). However, the substrate specificity differs between the two reactions; PE serves as the most preferred substrate for the hydrolysis, but PC and PS are better substrates than PE for the transphosphatidylation. In addition, the transphosphatidylation but not the hydrolysis of PE and PC is markedly activated on the addition of metal ions, especially Al3+. Nucleotide and amino acid sequence determination of the Stv. cinnamoneum PLD revealed the presence of common structural motifs identified in all PLD sequences from various species.

Reconstitution of GTP-gamma-S-dependent phospholipase D activity with ARF, RhoA, and a soluble 36-kDa protein

For activation of kidney membrane phospholipase D (PLD), cytosol is absolutely needed in addition to GTP-gamma-S. The active component of cytosol consists of three protein factors: ADP-ribosylation factor, RhoA, and a soluble 36-kDa protein. Any combination of these two factors synergistically activates PLD to some extent, but the presence of the three factors causes full activation. The 36-kDa protein is stable at 60 degrees C but inactivated at 80 degrees C for 10 min. Tissue distribution of the 36-kDa protein roughly coincides with that of PLD, suggesting physiological relevance of the protein in the regulation of PLD.

Mammalian phospholipase D: phosphatidylethanolamine as an essential component

Bovine kidney phospholipase D (PLD) was assayed by measuring the formation of phosphatidylethanol from added radioactive phosphatidylcholine (PtdCho) in the presence of ethanol, guanosine 5'-[gamma-thio]triphosphate, ammonium sulfate, and cytosol factor that contained small GTP-binding regulatory proteins. The PLD enzyme associated with particulate fractions was solubilized by deoxycholate and partially purified by chromatography on a heparin-Sepharose column. This PLD preferentially used PtdCho as substrate. After purification, the enzyme per se showed little or practically no activity but required an additional factor for the enzymatic reaction. This factor was extracted with chloroform/methanol directly from particulate fractions of various tissues, including kidney, liver, and brain, and identified as phosphatidylethanolamine (PtdEtn), although this phospholipid did not serve as a good substrate. Plasmalogen-rich PtdEtn, dioleoyl-PtdEtn, and L-alpha-palmitoyl-beta-linoleoyl-PtdEtn were effective, but dipalmitoyl-PtdEtn was inert. Sphingomyelin was 30% as active as PtdEtn. The results suggest that mammalian PLD reacts nearly selectively with PtdCho in the form of mixed micelles or membranes with other phospholipids, especially PtdEtn.

Mammalian phospholipase D: activation by ammonium sulfate and nucleotides

Phospholipase D (PLD) associated with the rat kidney membrane was activated by guanine 5'-[gamma-thio]triphosphate and a cytosol fraction that contained ADP-ribosylation factor. When assayed by measuring the phosphatidyl transfer reaction to ethanol with exogenously added radioactive phosphatidylcholine as substrate, the PLD required a high concentration (1.6 M) of ammonium sulfate to exhibit high enzymatic activity. Other salts examined were far less effective or practically inactive, and this dramatic action of ammonium sulfate is not simply due to such high ionic strength. Addition of ATP but not of nonhydrolyzable ATP analogue adenosine 5'-[beta, gamma-imido]diphosphate further enhanced the PLD activation approximately equal to 2- to 3-fold. This enhancement by ATP needed cytosol, implying a role of protein phosphorylation. A survey of PLD activity in rat tissues revealed that, unlike in previous observations reported thus far, PLD was most abundant in membrane fractions of kidney, spleen, and liver in this order, and the enzymatic activity in brain and lung was low.

Serum valproate concentrations in epileptic children with favourable responses

The lower limits of the "therapeutic range" for serum levels of sodium valproate (VPA) were evaluated in epileptic children showing a benign clinical course. Twenty-five outpatients, aged 5 to 16 years, whose seizures were well controlled over three years with VPA alone, were studied. Venous blood was taken 1.1 to 5 hrs after the morning dose. Serum VPA concentrations at steady-state after receiving the maintenance doses to control seizures were determined by enzyme immunoassay. The patients were divided into three groups according to the seizure type and the age at onset; A and B: patients with tonic and/or clonic seizures, aged below 3 yrs (n = 11) and 3 to 11 yrs (n = 6), respectively, C: those with absence seizures, aged 4 to 11 yrs (n = 8). The serum concentrations in A (47.8 +/- 21.6 micrograms/ml, mean +/- SD) were significantly (p less than 0.02) lower than those in groups B and C (85.2 +/- 14.0 and 73.0 +/- 17.4 micrograms/ml, respectively). VPA concentrations below 50 micrograms/ml were seen in 6 patients (55%) in group A. It was concluded that many epileptic children, whose ages at onset were below 3 yrs, with tonic and/or clonic seizures could be controlled even with low initial serum concentrations below the "therapeutic range".