• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.309-315
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• 1998

An extracellular levansucrase, which catalyzes the formation of levan from sucrose, from the culture broth of Zymomonas mobilis ZM1 was purified by conventional column purification methods. The final purification yield was 18.3 fold of the crude enzyme from Z. mobilis, with 16.5 % of the enzyme recovered in the preparation step. The molecular weight of the enzyme was estimated to be 91,000 by Superose 12 gel filtration, and 45,000 by SDS-PAGE, indicating that levansucrase is a dimer. The optimum pH for the enzyme activity was around pH 4.0 for sucrose hydrolysis, and was around pH 5.0 for levan formation. The enzyme was inhibited by some metal ions, such as Hg$\^$2+/ and Cu2$\^$2+/, and 50% of inhibition was observed with 5mM EDTA. The enzyme activity was enhanced by the presence of detergent Triton X-100, but inhibited by SDS completely The enzyme catalyzes the liberation of reducing sugars, oligosacccharides and the formation of fructose polymer(levan). The enzyme also catalyzes the transfructosylation reaction of fructose moiety from sucrose to various sugar acceptor molecules, including sugar alcohols.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1544-1549
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• 2008

MhMTS and MhMTH are trehalose ($\alpha$-D-glucopyranosyl-[1,1]-$\alpha$-D-glucopyranose) biosynthesis genes of the thermophilic microorganism Metallosphaera hakonensis, and encode a maltooligosyltrehalose synthase (MhMTS) and a maltooligosyltrehalose trehalohydrolase (MhMTH), respectively. In this study, the two genes were fused in-frame in a recombinant DNA, and expressed in Escherichia coli to produce a bifunctional fusion enzyme, MhMTSH. Similar to the two-step reactions with MhMTS and MhMTH, the fusion enzyme catalyzed the sequential reactions on maltopentaose, maltotriosyltrehalose formation, and following hydrolysis, producing trehalose and maltotriose. Optimum conditions for the fusion enzyme-catalyzed trehalose synthesis were around $70^{\circ}C$ and pH 5.0-6.0. The MhMTSH fusion enzyme exhibited a high degree of thermostability, retaining 80% of the activity when pre-incubated at $70^{\circ}C$ for 48 h. The stability was gradually abolished by incubating the fusion enzyme at above $80^{\circ}C$. The MhMTSH fusion enzyme was active on various sizes of maltooligosaccharides, extending its substrate specificity to soluble starch, the most abundant natural source of trehalose production.

• Journal of Microbiology and Biotechnology
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• v.9 no.1
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• pp.1-8
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• 1999

Most carbohydrates exist in nature in an insoluble state, which reduces their susceptibility towards various carbohydrases. Accordingly, they require intensive pretreatment for structural modification to enhance an enzyme reaction. The direct conversion of insoluble carbohydrates has distinct advantages for special types of reaction, especially exo-type carbohydrase; however, its application is limited due to structural constraints. This paper introduces two novel heterogeneous enzyme reaction systems for direct conversion of insoluble carbohydrates; one is an attrition coupled enzyme reaction system containing attrition-milling media for enhancing the enzyme reaction, and the other is a heterogeneous enzyme reaction system using extruded starch as an insoluble substrate. The direct conversion of typically insoluble carbohydrates, including cellulose, starch, and chitin with their corresponding carbohydrases, including cellulase, amylase, chitinase, and cyclodextrin glucanotransferase, was carried out using two proposed enzyme reaction systems. The conceptual features of the systems, their reaction characteristics and mechanism, and the industrial applications of the various carbohydrates are analyzed in this review.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.35-42
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• 2000

Reaction characteristics of 4-methylcatechol 2,3-dioxygenase (4MC230) purified from Pseudomonas putida SU10 with a higher activity toward 4-methylcatechol than catechol or 3-cethylcatechol were studied by altering their physical and chemical properties. The enzyme exhibited a maximum activity at pH 7.5 and approximately 40% at pH 6.0 for 4-methylcatechol hydrolysis. The optimum temperature for the enzyme was around $35^{\circ}C$, since the enzyme was unstable at higher temperature. Acetone(10%) stabilized the 4MC230. The effects of solvent and other chemicals (inactivator or reactivator) for the reactivation of the 4MC230 were also investigated. Silver nitrate and hydrogen peroxid severely deactivated the enzyme and the deactivation by hydrogen peroxide severely deactivated the enzyme and the deactivation by hydrogen peroxide was mainly due to the oxidation of ferrous ion to ferric ion. Some solvents acted as an activator and protector for the enzyme from deactivation by hydrogen peroxide. Ascorbate, cysteine, or ferrous ion reactivated the deactivated enzyme by hydrogen peroxide. The addition of ferrous ion together with a reducing agent fully recovered the enzyme activity and increased its activity abut 2 times.

• Food Science of Animal Resources
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• v.27 no.1
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• pp.102-109
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• 2007

Lactobacillus salivarius subsp. salivarius CNU27 possessed a high level of ${\alpha}$-galactosidase activity. Purified ${\alpha}$-galactosidase was obtained after sonication of harvested cell pellet followed by DEAE-Sephadex A-50 and Mono Q anion exchange chromatography. The specific activity of the purified enzyme was 8,994 units/mg protein which is 17.09 times higher than that in crude extract. The native enzyme was a monomer with a molecular mass of 56,397.1 dalton. The optimum temperature and pH for the enzyme were $40^{\circ}C$ and 6.0, respectively. The enzyme was stable between 25 and $50^{\circ}C$. However, ${\alpha}$-galactosidase activity was lost rapidly below pH 4.5 and above pH 8.5. The enzyme activity decreased to 6.73% and 4.30% of the original activity by addition of $Cu^{2+}$ and $Hg^{2+}$, respectively. Other metal compounds did not affect the enzyme activity significantly. The enzyme liberated galactose from melibiose, raffinose, and stachyose. The rate of substrates hydrolysis was measured by HPLC. Raffinose, stachyose and melibiose were completely decomposed after 24 hr at $40^{\circ}C$.

• KSBB Journal
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• v.13 no.2
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• pp.147-154
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• 1998

Enzymatic hydrolysis using an immobilized enzyme was carried out to produce chitosan oligosaccharides (COSs) from chitosan effectively. Chitosanase was immobilized on eight different carriers by physical adsorption. The enzyme immobilized on chitin had higher activity than those immobilized on the other carriers in spite of its lower adsorption. The activity of chitin-immobilized enzyme was more than 90% of the original activity. Optimal temperature of the immobilized enzyme increased by about $15^{\circ}C$ and its thermostability was excellent in relatively wide range of temperature. But its effects of pH did not improve compared to the free enzyme. The immobilized enzyme produced 153 mg/g chitosan of the reducing sugar for 3hrs of hydrolytic incubation time. The total content of higher oligomers, tetramer to hexamer, among amount of total COSs obtained for 2hrs was more than 90%. In kinetic parameters for both enzymes, immobilized enzyme showed lower affinity for substrate and reaction rate than free enzyme, however, no reduction of the rate for high substrate concentrations. Consequently, chitin-immobilized could effectively hydrolyse chitosan and produce the higher COSs without activity decrease in comparison with the free enzyme.

• BMB Reports
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• v.28 no.2
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• pp.94-99
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• 1995

The properties of binding sites in the active site of $Zn^{2+}$-glycerophosphocholine cholinephosphodiesterase were examined using substrates and inhibitors of the enzyme. Phosphodiesterase hydrolyzed p-nitrophenylphosphocholine, p-aminophenylphosphocholine, and glycerophosphocholine, but did not hydrolyze either acylated glycerophosphocholine or bis (p-nitrophenyl)phosphate, suggesting a size limitation for interaction with a glyceryl moiety-binding subsite. The hydrolysis of p-nitrophenylphosphocholine was competitively inhibited by glycerophosphocholine and p-aminophenylphosphocholine, while glycerophosphoethanolamine was a weak inhibitor. The enzyme was also inhibited by choline, but not by ethanolamine. Thiocholine, a much more potent inhibitor than choline, was more inhibitory than cysteamine, suggesting a strict specificity of an anionic subsite adjacent to a $Zn^{2+}$ subsite. Of all oxyanions tested, the tellurite ion was found to strongly inhibit the enzyme by binding to a $Zn^{2+}$ subsite. The inhibitory role of tellurite was synergistically enhanced by tetraalkylammonium salts, but not by glycerol. Deactivation of the enzyme by diethylpyrocarbonate was partially protected by choline, but not by glycerophosphate. It is suggested that the active site of phosphodiesterase contains three binding subsites.

• Journal of Life Science
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• v.6 no.2
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• pp.79-86
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• 1996

A bacterium producing pullulanase was from soil, and was identified Bacillus cereus and named as Bacillus cereus JK36. The optimal culture conditions for the efficident production of pullulanase from B. cereus JK36 was obtained by cultivating with the medium composed of 1% pullulan, 1% teast extract, 1% bactopeptone, 0.1% NaH$_{2}$PO$_{4}$, 2H$_{2}$O, 0.02% MgSO$_{4}$\ulcorner7H$_{2}$O at 40$\circ$C, initial pH 6.5 for 70 hours. Using the culture supernatant as crude enzyme, the optimal pH and temperature of the pullulanase of this strain were 6.5 and 50$\circ$C. In effect of pH and temperature on the stability of the enzyme, the enzyme was stable in the range of pH6.0$\sim$9.5 and up to 40$\circ$C, respectively. The hydrolysis product on pullulan was mainly maltotriose.

• Food Science of Animal Resources
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• v.37 no.5
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• pp.646-653
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• 2017

Alcalase hydrolysis of liquid egg white was used to produce 5-hydroxytryptophan (HTP) under various conditions and investigate the sleep-potentiating activity of liquid egg white hydrolysate (LEH) on pentobarbital-induced sleep. Alcalase hydrolysis yielded the highest content of 5-HTP ($13.50{\mu}g/mL$), while neutrase hydrolysis showed the lowest 5-HTP content ($5.23{\mu}g/mL$). The liquid egg white to water ratio (1:1) was optimal for the production of 5-HTP with high amino-nitrogen (A-N) content and degree of hydrolysis. The 5-HTP, amino-nitrogen, and degree of hydrolysis increased until 24 h of hydrolysis and slightly increased thereafter during hydrolysis with 2% and 5% enzyme addition. 5-HTP administration at doses of 6 and 9 mg/kg significantly increased sleep duration and decreased sleep latency time compared to that in the control (p<0.05). LEH (150 mg/mouse), which was equivalent to 5-HTP at 6 mg/kg, significantly decreased sleep latency time and increased sleep duration time compared to that in the control (p<0.05). Oral administration of LEH showed sleep-potentiating effects because of 5-HTP. The sleep-potentiating activity of LEH may have occurred through 5-HTP in our pentobarbital-induced sleep model. LEH may be a valuable alternative to sleep enhancement and may be used as a sleep-potentiating agent.

• Journal of Sericultural and Entomological Science
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• v.18 no.2
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• pp.101-105
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• 1976

The study was carried out to investigate the variations in the fibroin hydrolysis of leading silkworm varieties in Korea, and the relationship between the fibroin hydrolysis of the silkworm varieties with some characteristics and silk morphological property. The results obtained are summarized as follows: 1) The fibroin hydrolyzing ratio of both parent silkworm cocoons was reduced in the F$_1$hybrids. 2) A positive corelation (r=＋0.86) was approved between the mid-parent value and the F$_1$hybrid in the fibroin hydrolysis. 3) It was disclosed that the fibroin hydrolyzing ratio of Jam 103${\times}$Jam 104 was the lowest among the leading silkworm F$_1$hybrids. 4) The fibroin hydrolysis was affected by the silk morphological property, showing a positive corelation between the size of cocoon filament and the fibroin hydrolyzing ratio. 5) It was thought that the determination of the fibroin hydrolyzing ratio was useful as a marker for the selection of its related economical characters in silkworm breeding, because the fibroin hydrolysis of parents silkworm cocoons was heritable in their F$_1$hybrids.