Materials for the fungus flora of Japan (49)

Two interesting microfungi are described as new to Japan:Talaromyces galapagensis (anam.Penicillium galapagense), isolated from soil in Shizuoka; andPenicillium megasporum, isolated from marine sludge in Nagasaki. Some observations are recorded, particularly on ascomatal initials ofT. galapagensis, which are similar to those described forTalaromyces flavus.(48): Kaneko, S., Mycoscience 36: 359–360, 1995.     

Inhibitors and activators of ADP-ribosylation reactions

ADP-ribosylation reaction, that is the transfer of the ADP-ribose moiety of NAD⁺ to acceptor protein, is catalyzed by two classes of ADP-ribosyltransferases,i.e., poly(ADP-ribose) synthetase and mono (ADP-ribosyl)transferases. These two types differ not only in the number of transferring ADP-ribose units but also in the acceptor amino acid(s) and protein. Their in hibitors, particularly those of poly(ADP-ribose) synthetase, have been successfully employed in studies on biological functions of the enzymes and other related fields of research. Recently, we found many potent and specific inhibitors of poly-(ADP-ribose) synthetase, and broadened their chemical as well as biochemical variety. More recently, we found several potent inhibitors of arginine-specific mono(ADP-ribosyl)transferases and activators of poly(ADP-ribose) synthetase.     

Temperature-dependent effects of high pressure on the bioluminescence of firefly luciferase.

This study measured the effect of high pressure on the enzyme kinetics of firefly luciferase. When firefly luciferase is mixed with luciferin and ATP, a transient flash of light is produced, followed by a weak light, lasting hours. The first stage reaction produces an enzyme-luciferin-AMP complex and pyrophosphate. Addition of pyrophosphate to the reaction mixture decelerated the reaction rate, and the initial flash was prolonged to a plateau, showing a quasi-equilibrium state. The effects of temperature and pressure were analyzed at the plateau. The temperature scan showed that the maximum light intensity was observed at about 22.5 degrees C. When pressurized below the temperature optimum, pressure decreased the light intensity, while increasing it above the temperature optimum. According to the theory of absolute reaction rate, the following values were obtained for the bioluminescent reaction: delta V++ = 823.7 - 2.8 T cm3/mol and delta V = -280.47 + 0.94T cm3/mol, where T is the absolute temperature, delta V++ and delta V are, respectively, activation volume and the volume change due to thermal unfolding. The optimal temperature for the maximum light output occurs because the reaction rate increases with the temperature elevation at low temperature range, but the thermal unfolding of the enzyme decelerates the reaction velocity when the temperature exceeds a critical value. The intensity of luminescence is modified by the influence of pressure on both delta V++ and delta V. So long as the volume of the activated complex (V++) exceeds the average volume of the nonactivated complex (VN), pressure will slow down the reaction. At the point where the volumes become equal, there is no change in the rate under pressure. When the volume of the activated complex is less than that of the reactants, pressure will speed up the rate. This study showed that firefly luciferase is not exceptional to other enzymes in responding to high pressure.     

Lysophosphoinositide-specific phospholipase C in rat brain synaptic plasma membranes

A membrane preparation from rat brain catalyzed the hydrolysis of [2-³H]glycerol-labeled lysophosphatidylinositol (lysoPI) to yield monoacylglycerol (MG) and inositolphosphates. This phospholipase C activity had an optimal pH of 8.2. The membrane preparation did not require the addition of Ca²⁺ for its maximum activity, but the activity was inhibited by addition of 0.1 mM EDTA to the assay mixture and was restored by simultaneous addition of 0.2 mM Ca²⁺. The activity was found to be localized in synaptic plasma membranes prepared by Ficoll and Percoll density gradients. The phospholipase C was highly specific for lysoPI; diacylglycerol formation from phosphatidylinositol, and MG formation from lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylserine were below 5% of that observed with lysoPI under the conditions used. We concluded that there is a pathway for phosphatidylinositol metabolism in brain synaptic membranes which is different from the well-characterized phosphoinositide-specific phospholipase C pathway.Abbreviations PI phosphatidylinositol - lysoPI lysophosphatidylinositol - lysoPI-PLC lysophosphoinositide-specific phospholipase C - PI-PLC phosphoinositide-specific phospholipase C - MG monoacylglycerol - PLC phospholipase C To whom to address reprint requests.     

Molecular phylogeny in the Lardizabalaceae

Eleven species belonging to seven genera in the Lardizabalaceae were analyzed in terms of restriction fragment length polymorphism (RFLP) of chloroplast DNA and the sequence of the chloroplast gene,rbcL, of Lardizabalaceae and its related families. Phylogenetic trees inferred from parsimony, neighbor joining and maximum likelihood methods based on RFLP data showed that two South American genera,Boquila andLardizabala, and three East Asian genera,Akebia, Holboellia andStauntonia are closely related to each other, respectively. On the other hand, the parsimony, neighbor joining and maximum likelihood trees constructed using sequence data of therbcL gene showed thatAkebia, Stauntonia, Boquila andLardizabala clustered as(((Akebia, Stauntonia), Boquila), Lardizabala). This difference may be attributable to fewer informative sites inrbcL genes than in RFLP in this family.Decaisnea diverges at the very base of the Lardizabalaceae.     

The kinetics of end-product inhibition of l-lactate production from xylose and glucose by Lactococcus lactis IO-1

Summary The relative contributions of lactate inhibition and the generation of sterile (undividing) cells to the low xylose utilisation rate of Lactococcus lactis IO-1 was investigated. The lactate inhibition constant of xylose grown cells was shown to be 9.3 times more than that of glucose grown cells. However, the sterile cell production rate and LDH inactivation rate of the xylose cultures were at least 10 times less than the glucose cultures. Thus, it is suggested that the slower substrate consumption rate in xylose medium is caused mainly by the large inhibition constant for the end product.     

A newCercophora with aChrysosporium-like anamorph

A new species ofCercophora, isolated from river sediment collected from Sakai River in Nagasaki Prefecture, Japan, is described and illustrated. It is distinguished from the other knwon species by the morphology of its ascomatal peridium and ascospores, and by itsChrysosporium-like anamorph.     

Newly established cell lines fromDrosophila larval CNS express neural specific characteristics

Summary From the central nervous system ofDrosophila melanogaster 3rd instar larvae, eight continuous cell lines have been established (named ML-DmBG1 to 8). Using ML-DmBG2, single colony isolation was carried out and six colonial clones were obtained. All reacted to the antibody to horseradish peroxidase, which is a neuronal marker in insects. Acetylcholine, a known neurotransmitter inDrosophila, was detected in three of the colonial clones by high performance liquid chromatography. Therefore, it is concluded that the established colonial clones are neural cells originating in the larval central nervous system. Among them, some variation was observed with respect to morphology, acetylcholine content, and reactivity to anti-HRP. The variation may reflect the heterogeneity of cells composing the central nervous system.