• KSBB Journal
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• v.26 no.4
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• pp.300-304
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• 2011

Phytases are hydrolytic enzymes that catalyze the sequential hydrolysis of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate) to myo-inositols with lower numbers of phosphate groups. Two types of phytases have been identified which initiate hydrolysis of the phytic acid at either the 3- or 6- position of the inositol ring. In the present investigation, a mathematical model was proposed and computed to estimate maximum enzyme reaction rate constants which fit the experimental data obtained by other authors. Although the data points were scattered to some extent, good agreement was found between the model and the experiment data. It appears that the maximum rate constants of removal of the first, second, and third phosphate groups were not equal. Also there was neither a steady trend upward or downward in the rate constants with the stepwise hydrolysis reactions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.6
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• pp.1143-1147
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• 1998

Enzymatic characterization of peroxidase(E.C. 1.11.1.7) from soybean sprouts was investigated. The optimum pH of the purified peroxidase was 7.0 and relatively stable at pH 6.0~7.0. And the optimum temperature was 50oC. The enzyme was most active with guaiacol as a substrate, followed by (＋)catechin, pyrogallol and p phenylenediamine. The Km values for guaiacol and H2O2 were 4.2mM and 2.5mM, respectively. L Ascorbic acid and 2 mercaptoethanol greatly inhibited the enzyme activity, while Cu2+, Co2+ and Ni2+ activated the enzyme.

• Microbiology and Biotechnology Letters
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• v.23 no.4
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• pp.416-424
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• 1995

Mechanism of the cyclodextrin (CD) production reaction by cyclodextrin glucanotransferase (CGTase) using swollen extrusion starch as substrate was investigated emphasizing the structural features of starch granule. The degree of gelatinization was identified to be the most representative structural characteristic of swollen starch. The most suitable degree of gelatinization of swollen starch for CD production was around 63.52%. The structural transformation of starch granule during enzyme reaction was also followed by measuring the changes of the degree of gelatinization, microcrystallinity, and accessible and inaccessible portion to CGTase action of residual swollen starch. The adsorption phenomenon of CGTase to swollen starch was also examined under various conditions. The inhibition mechanism of CGTase by various CDs was identified to be competitive, most severely by a-CD. The mechanism elucidated will be used for development of a kinetic model describes CD production reaction in heterogeneous enzyme reaction system utilizing swollen extrusion starch.

• BMB Reports
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• v.34 no.1
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• pp.39-42
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• 2001

Previous studies indicate that B. subtilis protoporphyrinogen oxidase is poorly inhibited by diphenyl ether herbicides. To better understand the basis of this insensitivity, the enzyme was overexpressed as a soluble protein in E. coli, purified and characterized. The mechanism of oxidation of B. subtilis protoporphyrinogen IX was studied and the enzyme kinetic parameters were determined for protoporpyrinogen IX; $K_m$, and $k_{cat}$ were $6.3\;{\mu}M$ and $0.028\;h-^1$, respectively. The enzyme required flavin adenine dinucleotide as a cofactor and its activity was enhanced by 1 mM n-octylglucopyranoside. The nonenzymatic oxidation rate was dependent on the concentration of protoporphyrinogen IX, suggesting that the reaction involves a pre-equilibrium step followed by a rate-limiting step.

• BMB Reports
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• v.31 no.6
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• pp.548-553
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• 1998

A minor anionic isoperoxidase named $A_{3n}$, was isolated from Korean radish (Raphanus sativus L.) root. Purification of the enzyme was accomplished by CMcellulose chromatography, DEAE-Sephacel chromatography, and Sephadex G-75 gel filtration. The enzyme was a glycoprotein with molecular weight of approximately 31,000 as determined by SDS-PAGE and 33,000 by Sepadex G-150 gel filtration, which is by far the smallest among the reported isoperoxidases. The pI value was 3.5. The optimum pH of the enzyme was 6.5 for guaiacol and $H_2O_2$, and the $K_m$ values for guaiacol and $H_2O_2$ were 13.3 mM and 1.5 mM, respectively. Kinetic studies with various substrates revealed that only A3n, unlike other isoperoxidases from radish, did not use scopoletin as a substrate and had very low $K_m$ value of 0.25 mM for ferolic acid among naturally occurring phenolic substrates.

• BMB Reports
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• v.29 no.4
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• pp.294-299
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• 1996

Glyoxalase I (Ee 4.4.1.5, lactoylglutathione lyase) from Chlamydomonas reinhardtii was purified to homogeneity by ammonium sulfate fractionation, anion-exchange chromatography, hydrophobic interaction chromatography, and affinity chromatography on S-hexylglutathione agarose. The purified enzyme was judged to be homogeneous on SDS-PAGE, and consisted of a single polypeptide chain with a relative molecular weight of 24,000. The enzyme was most active at $40^{\circ}C$ and pH 7.5. It was catalytically most active with methylglyoxal as substrate. A number of properties of the Chlamydomonas glyoxalase I enzyme, such as substrate specificity, molecular mass, kinetic parameters, pi, metal ion effect, have been determined and compared with those reported for preparations from other sources. It had somewhat different characteristics from mammalian enzymes.

• Journal of Microbiology
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• v.35 no.1
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• pp.15-20
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• 1997

Kinetic studies were done to elucidate the reaction mechanism of purine nucleoside phosphorylase (PNP) in Micrococcus Luteus. PNP catalyzes the reversible phosphorolysis of ribonucleosides to their respective base. The effect of alternative competing substrates suggested that a single enzyme was involved in binding to the active site for all purine nucleosides, inosine, deoxyiosine, guanosine, deoxyguanosine, adenosine and deoxyadenosine. Affinity studies showed that pentose moiety reduced the binding capacity and methylation of ring N-1 of inosine and guanosine had little effect on binding to bacterial enzyme, whereas these compounds did not bind to the mammalian enzymes. The initial velocity and product inhibition studies demonstrated that the predominant mechanism of reaction was an ordered bi, bi reaction. The nucleoside bound to the enzyme first, followed by phosphate. Ribose 1-phosphate was the first product to leave, followed by base.

• KSBB Journal
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• v.5 no.2
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• pp.107-112
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• 1990

The kinetic characteristics of an invertase immobilized covalently on porous silica have been appraised for the applicability of porous silica to immobilization supports of enzymes. The invertase was covalently bound with glutaraldehyde on 3-aminopropyltriethoxy-silane-activated porous silica to give a maximum loading of 120mg invertase per 1 gram of dry silica and 26.9 to 70.2% retention of original activity. The porous structure of silica seems to be suitable for enzyme immobilization, judging from the observed results of high immobilization capacity and comparably satisfactory retention of enzyme activity.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.65-68
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• 2003

The paper discusses the use of stable emulsion, prepared by membrane emulsification technology, to improve the enantiocatalytic performance of immobilised lipase in multiphasic membrane reactors. The production of optical pure (S)-naproxen from racemic naproxen methyl ester has been used as model reaction system. The enzyme was immobilised in the sponge layer (shell side) of capillary polyamide membrane with 50 kDa cut-off, The O/W emulsion, containing the substrate in the organic dispersed phase, was fed to the enzyme membrane reactor from shell-to-lumen. The results evidenced that lipase maintained stable activity during all the operation time (more than 250 hours), showing an enantiomeric excess (96 $\pm$2%) comparable to the free enzyme (98 $\pm$ 1%) and much higher compared to similar lipase-loaded membrane reactors used in two-separate phase systems (90%). The study showed that immobilised enzymes can achieve high stability as well as high catalytic activity and enantioselectivity.

• Microbiology and Biotechnology Letters
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• v.18 no.1
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• pp.39-43
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• 1990

The inhibitor had the inhibitory activities against hydrolysis of PNPG, sucrose and ONPG by $\alpha$-Dglucosidase, $\alpha$ - and $\beta$ -galactosidase, but it did not inhibit amylases and other carbohydrases. Kinetic studies exhibited that the inhibitory substance non-competitively inhibited the enzyme reaction with a Ki value of 118 $\mu$g/m$\ell$, and enzyme-inhibitor complex was formed slowly.