High-level secretory production of phospholipase A1 by Saccharomyces cerevisiae and Aspergillus oryzae

Phospholipase A1 (PLA1) is a hydrolytic enzyme that catalyzes the removal of the acyl group from position 1 of lecithin to form lysolecithin. The PLA1 gene, which had been cloned from Aspergillus oryzae, was expressed in Saccharomyces cerevisiae and A. oryzae. Through the modification of the medium composition and the feeding conditions of substrate, the production level of PLA1 by S. cerevisiae was increased to a level fivefold higher than that indicated in a previous report. In the case of A. oryzae, introduction of multicopies of PLA1 expression units, and the morphological change from the pellet form to the filamentous form were effective for the enhancement of PLA1 production. We succeeded in producing 3,500 U/ml of PLA1 using an industrial-scale fermentor.     

Antioxidative effects of fluvastatin and its metabolites against oxidative DNA damage in mammalian cultured cells

We investigated the effects of fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on reactive oxygen species (ROS) and on oxidative DNA damage in vitro, as well as the effects of the main fluvastatin metabolites (M2, M3, and M4) and other inhibitors of the same enzyme, pravastatin and simvastatin. The hydroxyl radical and the superoxide anion scavenging activities of fluvastatin and its metabolites were evaluated using an electron spin resonance spectrometer. Fluvastatin and its metabolites showed superoxide anion scavenging activity in the hypoxanthine-xanthine oxidase system and a strong scavenging effect on the hydroxyl radical produced from Fenton's reaction. Protective effects of fluvastatin on ROS-induced DNA damage of CHL/IU cells were assessed using the single-cell gel electrophoresis assay. CHL/IU cells were exposed to either hydrogen peroxide or t-butylhydroperoxide. Fluvastatin and its metabolites showed protective effects on DNA damage as potent as the reference antioxidants, ascorbic acid, trolox, and probucol, though pravastatin and simvastatin did not exert clear protective effects. These observations suggest that fluvastatin and its metabolites may have radical scavenging activity and the potential to protect cells against oxidative DNA damage. Furthermore, ROS are thought to play a major role in the etiology of a wide variety of diseases such as cellular aging, inflammation, diabetes, and cancer development, so fluvastatin might reduce these risks.     

Infectivity of different genotypes of human Blastocystis hominis isolates in chickens and rats

Most Blastocystis hominis isolates from humans are believed to be potentially zoonotic. This is because B. hominis isolates found in a variety of other host species have been found to have identical or relatively similar genotypes to those found in human isolates. However, the transmission of human B. hominis isolates to other animals has not been confirmed experimentally. In this study, the infectivity associated with several unique human Blastocystis genotypes (subtypes 2, 3, 4 and 7) was therefore investigated by infecting chickens and rats with two isolates of each subtype experimentally. The results showed that one isolate of subtype 4 and one isolate of subtype 7 was capable of infecting both chickens and rats, while two isolates of subtype 2, another isolate of subtype 4, and another isolate of subtype 7 could only infect chickens. Conversely, two isolates of subtype 3 failed to infect either of the animals. These results confirmed that several genotypes from human isolates could infect chickens and/or rats, indicating that chickens and rats are suitable experimental animal models for studying the zoonotic potential of human Blastocystis isolates.     

Kinetic analysis of microbial desulfurization of model and light gas oils containing multiple alkyl dibenzothiophenes

The reaction mechanism of biodesulfurization was investigated using whole cells of Rhodococcus erythropolis KA2-5-1, which have the ability to convert dibenzothiophene (DBT) into 2-hydroxybiphenyl. The desulfurization patterns of alkyl DBTs were represented by the Michaeis-Menten equation. The values of rate constants, the limiting maximal velocity (Vmax) and Michaelis constant (Km), for desulfurization of alkyl DBTs were calculated. The relative desulfurization activities of various alkyl DBTs were reduced in proportion to the total carbon numbers of alkyl substituent groups. Alkyl DBTs that had a total of six carbons of alkyl substituent groups were not desulfurized. The type or position of alkyl substituent groups had little effect on desulfurization activity. The desulfurization activity of each alkyl DBT, when mixed together, was reduced. This phenomenon was caused by apparent competitive inhibition of substrates. Using the apparent competitive inhibition model, the desulfurization pattern of a multiple components system containing alkyl DBTs was elucidated. This model was also applicable for biodesulfurization of light gas oil.     

Differences in liver homogenates from Donryu, Fischer, Sprague-Dawley and Wistar strains of rat in the drug-metabolizing enzyme assay and the salmonella/hepatic S9 activation test

Comparison studies for detecting differences between liver microsome and S9 preparations from 4 strains (Donryu, Fischer, Sprague-Dawley, Wistar) of young male rats were carried out with pretreatment of the animals by inducers such as PCBs and PB plus 5,6-BF. Each microsome fraction was assayed for the enzymic activity of metabolism of model substrates such as aniline, benzophetamine, BP, DMN and 7-ethoxycoumarin. The hepatic S9 sample was also compared, as regards its metabolizing ability to activate 9 pre-mutagens (2AA, AAF, o-AAT, BP, DAB, DMBA, DMN, m-PDA, quinoline) to directly acting mutagens in the Salmonella/hepatic S9 activation test by using TA98, TA100 and TA1537 strains with or without cytochrome P450 inhibitors (SKF-525A, metyrapone, 7,8-benzoflavone).In the enzymic assay with PCBs-induced microsomes, BP hydroxylation revealed a strain-specific difference: the microsomes from Fischer and Wistar rats were more effective for metabolizing BP than those from the other strains of rat. The effect of induction by PB plus 5,6-BF for Fischer rats showed relatively higher enzymic activity in the same induction group. Other microsomes prepared from rats with and without induction by PB plus 5,6-BF did not show a clear-cut strain dependency in the enzymic activities assayed.In the mutation experiments with hepatic S9 samples, the examination of DAB and quinoline revealed a marked strain difference when S9 samples prepared from PCBs-pretreated and PB-plus-5,6-BF-induced rats were used: the S9 sample from Fischer rats was available for activating the two pre-mutagens to directly acting mutagens. No marked difference in the metabolic activation of the remaining 7-pre-mutagens was observed on other S9 preparations.In examinations of mutagenicity activities with the use of three inhibitors, the two S9 preparations made with the two induction methods showed inhibition profiles closely similar to each other. However, there were minor differences in the profiles by these inhibitors.From these findings it was concluded that Fischer rat-liver S9 is useful for detecting mutagens in the metabolic activation test, when induction by PB plus 5,6-BF was used in the Ames Salmonella test.     

Ascorbic acid induces a marked conformational change in long duplex DNA.

Ascorbic acid is often regarded as an antioxidant in vivo, where it protects against cancer by scavenging DNA-damaging reactive oxygen species. However, the detailed mechanism of the action of ascorbic acid on genetic DNA is still unclear. We examined the effect of ascorbic acid on the higher-order structure of DNA through real-time observation by fluorescence microscopy. We found that ascorbic acid generates a pearling structure in single giant DNA molecules, with elongated and compact regions coexisting along a molecular chain. Results from electron microscopy and atomic force microscopy indicate that the compact regions assume a loosely packed conformation. A possible mechanism for the induction of this conformational change is discussed in relation to the interplay between the higher-order and second-order structures of DNA.     

New Rev-export inhibitor from Alpinia galanga and structure–activity relationship

Bioassay-guided separation by use of the fission yeast expressing NES of Rev, an HIV-1 viral regulatory protein, disclosed 1′-acetoxychavicol acetate (ACA, 1) as a new inhibitor for nuclear export of Rev from the roots of Alpinia galanga. Both analysis for mechanism of action with biotinylated probe (2) and several synthesized analogs established crucial portions in 1 for Rev-export inhibitory activity.