Studies on γ-Radiolysis of Sulfur Containing Amino Acids

In connection with flavor deterioration accompanied by food irradiation, the effect of γ-irradiation on sulfoxide amino acids in air free aqueous system was investigated. The major radiolysis products from S-n-propyl-l-cysteine sulfoxide (PCSO) were alanine, cysteic acid, dipropyl disulfide, etc., and from S-allyl-l-cysteine sulfoxide (ACSO) were S-allyl-l-cysteine, cystine, cysteic acid, etc., which were isolated chromatographycally and identified by using IR and mass spectrometry. The sulfoxide in ACSO was more easily reduced to sulfide than that of in PCSO, and the bond of S-C (β-carbon in alanine moiety) in ACSO was difficult to cleave. These differences observed between PCSO and ACSO in the radiolysis products and their yields indicate that the radiolysis degradation is considerably influenced by the structure of alkyl group. From the experiments with N₂O or KBr addition during irradiation, principal roles of the active species in irradiated water in the degradation processes were partly elucidated.     

Purification and Properties of Lytic, β-1, 3-Glucanase from Flavobacterium dormitator var. glucanolyticae

An endo β-1, 3-glucanase which is able to disrupt the cells of living yeast has been purified in homogeneous state from the culture filtrate of Flavobacterium dormitator var. glucanolyticae. The molecular weight of the enzyme was estimated to be 17,000 ~ 22,000. The mode of enzyme action has been suggested to be a “random” type of β-1, 3-glucanase. The enzyme preferes larger chains saccharides as substrate for its action, however, smaller oligosaccharides such as laminaritriose and laminaribiose are also decomposed by the enzyme. The Km values of the enzyme for laminarin, laminarihexaose, and laminaritetraose were determined to be 0.26, 1.18, and 2.00 g/liter, respectively. The ability of this enzyme to disrupt the cells of living yeast is its remarkable point, since endo β-1, 3-glucanase of a smaller oligosaccharide-producing type from most sources has been recognized to be inactive (or very weakly active) on living yeast cells.     

Determination of 2-Aminoethylphosphonic Acid and Its Y-iM ethyl Derivative in Animal Tissues by Gas Chromatography with Flame Photometric Detection

A sensitive and selective method was developed for the determination of 2-aminoethylphosphonic acid (AEP) and W-methyl AEP in animal tissues by gas chromatography (GC). These compounds were converted into their A-isobutoxycarbonyl methyl ester derivatives and measured by GC with flame photometric detection (FPd-GC), using 0.5 % FFAP on Uniport HP as the GC column packing. The calibration curves for AEP and A-methyl AEP in the range of 0.02 ~ 2 μg were linear, and the detection limit was about 20 pg as an injection amount. AEP and A^-methyl AEP in animal tissues were found in the free form and bound form with lipid and other biological macromolecules, and they could be measured without any influence from coexistent substances by FPd-GC. The recoveries of AEP and A'-methyl AEP added to the tissue samples were 92 —105 %, and their reproducibility was found to be satisfactory. The distribution of these compounds in various animals was also studied by using this new method.     

Biological Activities of Fundamental,Carbohydrate Skeleton of Lipid A Containing Amide-linked 3-Hydroxytetradecanoic Acid

In the initial stage of hydrolysis, exo-ß-(l-→3)-d-glucanase from Basidiomycetes sp. QM 806 cleaved laminaran from Eisenia bicyclis with a pattern resembling an endo-hydrolase. Five kinds of intermediate gluco-oligosaccharides were separated by a combination of gel filtration and HPLC. They were shown to be 3²-O-ß-d-glucosyl-gentiobiose, 3²-O-ß-d-gentiobiosyl-gentiobiose, 3³O-ß-d-glucosyl-gentiotriose, 3⁴-ß-d-glucosyl-3²-O-gentiobiosyl-gentiobiose, and 3³-O-ß-d-gentio-biosylgentiotriose by enzymic hydrolysis and methylation analysis as well as by ¹³C NMR spectroscopy. As a result, such kinds of ß-(l → 3)-ß-(l→6)-linked oligosaccharides could be accounted for in the initial cleavage, and they were hydrolyzed ultimately to glucose, gentiobiose, and gentio-triose. It suggests that a single (1 → 3)-linkage on a block of (1 → 6)-links show some resistance to attack by this enzyme.     

Isolation of Triterpenoid Glycosides (Saikosaponins) from Bupleurum polyclonum Y. Li et S. L. Pan and Their Chemical Structures

Sixteen triterpenoid glycosides, named S13 to S25, S37, S38 and S40, were isolated from the root of Bupleurum polyclonum Y. Li et S. L. Pan, and their structures were determined from NMR spectral analyses. Among them, S24, S37 and S38 were found to be new substances, their structures being established as 30-β-d-glucopyranosyl 30-hydroxysaikosaponin-b₂, 2″-O-acetylsaikosaponin-b₂ and 3″-O>-acetylsaikosaponin-b₂, respectively.     

Changes in Flavor Components of Onion by γ-Irradiation

The effect of γ-irradiation on the flavor of Onions (Senshu Yellow) associated with sprout-inhibition has been investigated. The relative amounts of propionaldehyde, n-propyl mercaptan and di-n-propyl disulfide in onions stored for 0, 5, 10, 20 and 30 days, respectively, after irradiation were estimated by measurement of peak areas of gas chromatograms. It was observed that the lachrymatory character and the pungent flavor had been decreased by γ-irradiation (remarkably at 70 and 700 Krads). In this connection, the amounts of propionaldehyde and di-n-propyl disulfide were decreased with increasing radiation dose and storage period at room temperature (20 to 25°C) and at low temperature (4°C). Moreover, it was observed that the sweetness had been decreased by γ-irradiation, but the amount of n-propyl mercaptan was increased with radiation dose and storage period. Therefore it seems that there is no correlation between the sweetness of onion and the amount of n-propyl mercaptan.     

Isolation and Characterization of a Temperature-sensitive Sporulation Mutant of Bacillus subtilis

Temperature-sensitive sporulation mutants were isolated spontaneously from Bacillus subtilis 168 TT by a sequential transfer method. A representative mutant strain, ts32, was characterized in detail. The mutant grew normally at 30°C and 42°C, but did not sporulate at 42°C. Electron microscopic observation and physiological analysis showed that the mutant was blocked at stage 0-1 of sporulation. Genetic analysis suggested that the mutation was located at the spo0B locus on the B. subtilis chromosome. Temperature-shift experiments clearly showed that the spo0B gene product functions only at the beginning of sporulation.