• Journal of Life Science
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• v.24 no.2
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• pp.118-127
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• 2014

The kinetic properties and isozyme expression of lactate dehydrogenase (EC 1.1.1.27; LDH) in tissues from Rana catesbeiana I and II collected from February (I) and August (II) were studied. LDH activities, A4 isozyme, and LDH/citrate synthase (EC 4.1.3.7; CS) were high in skeletal muscle from R. catesbeiana I, and LDH $B_4$ isozyme increased in several tissues of R. catesbeiana II. In particular, LDH activities were high in heart and brain tissues from R. catesbeiana II. LDH eye-specific C isozyme, detected by native polyacrylamide gel electrophoresis after immunoprecipitation, was expressed in eye tissue and was more similar to the $B_4$ than $A_4$ isozyme. LDH $A_4$ isozyme was purified by oxamate-linked affinity chromatography, and the molecular weight of subunit A was 32.0 kDa. In R. catesbeiana II, levels of $Km^{PYU}$, $Vmax^{LAC}$, and tolerance to lactate of LDH were high in all tissues, and $Vmax^{PYU}$ of LDH in heart and brain tissue was highly detected. Purified $A_4$ isozyme and LDH in eye tissue were highly tolerate compared to others. The $Km^{LAC}$ value was highly measured compared to $Km^{PYU}$. The degree of inhibition by 10 mM of pyruvate on LDH activities in tissues from R. catesbeiana I and II was more pronounced as the ratio of subunit B increased. As a result, characteristic expression of LDH eye-specific C was found in R. catesbeiana. Anaerobic metabolism seemed to predominate as the LDH of skeletal muscle from I showed higher activity. It also appeared that R. catesbeiana II adapted well to incremental increases in LDH B, becoming tolerant to the lactate of LDH in tissues.

• The Korean Journal of Food And Nutrition
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• v.9 no.4
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• pp.372-378
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• 1996

The effects of branched chain amino acids and metabolites in growth media on the biosynthesis of Serratia marcescens threonine dehydratase activity were examined. The enzyme activity was decreased above 60% by leucine among the range from 1 to 20 mM, and the enzyme activity was decreased approximately 20% by a low concentration of valine (1 to 4 mM), but not affected at high concentration (20 mM). However, the enzyme activity was increased approximately 100 to 140% by a low concentration of isoleucine (1 to 4 mM), but decreased approximately 25 to 80% at high concentration (15 to 30 mM). The enzyme activity was decreased by 25 and 58% by the simultaneous addition of all three branched chain amino acids at 2 and 10 mM concentration, respectively, but increased by 75 and 50% by the combination addition of isoleucine plus valine and isoleucine plus leucine at 2 mM, respectively. cAMP was decreased the enzyme activity approximately 10 to 40% by a low concentration (1 to 2 mM), but increased by 80% at high concentration (10 mM). These data suggest that S. marcescens threonine dehydratase should be multivalently repressed by branched chain amino acids, but positively regulated by a low isoleucine concentration and may play a regulatory role in an isoleucine biosynthetic pathway unlike the E. coli K-12 enzyme.

• Journal of Soil and Groundwater Environment
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• v.9 no.3
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• pp.49-55
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• 2004

A soil enrichment LYF-1 culture from a contaminated site, which could reductively dechlorinate 900 $\mu$M (ca. 150 mg/L) of tetrachloroethylene (PCE) stoichimetrically into cis-1,2-dichloroethylene (cis-DCE), was established and characterized. The enrichment culture can use yeast extract, peptone, formate, acetate, lactate, pyruvate, citrate, succinate, glucose, sucrose, and ethanol as electron donors for dechlorination of PCE. Addition of NO$_2$$^{[-10]}$ and NO$_3$$^{[-10]}$ as alternative electron acceptors showed complete inhibition of PCE dechlorination, but S$_2$O$_3$$^{-2}$ , SO$_3$$^{-2}$ and SO$_4$$^{-2}$ had no significant effect on PCE dechlorination. The enrichment culture was attached to ceramic media in an anaerobic fixed-bed reactor. The fixed-bed reactor showed more than 99％ of PCE degradation in the range of PCE loading rate of 0.13-0.78 $\mu$moles/L/hr. The major end product of PCE dechlorination was cis-DCE.

• Journal of Life Science
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• v.26 no.2
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• pp.155-163
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• 2016

Metabolism of lactate dehydrogenase (EC 1.1.1.27, LDH) was studied to identify the function of LDH-C. Tissues of LDH liver-specific Ldh-C expressed Carassius auratus and eye-specific Ldh-C expressed Lepomis macrochirus after starvation were studied. LDH activity in liver tissue from C. auratus was increased after starvation. And LDH specific activity (units/mg) and LDH/CS were increased in tissues. It means the anaerobic metabolism was taking place in C. auratus after starvation. LDH B₄ isozyme was decreased in skeletal muscle and increased in heart tissue. LDH C₄ isozymes those showed in eye and brain tissues were identified as liver-specific C₄ isozymes and disappeared after starvation. And C hybrid in eye, A₄ isozyme in brain, and both C hybrid and C₄ isozyme in liver tissue were increased, respectively. In L. macrochirus, the level of variation of LDH activities was low but greatly increased especially in eye tissue and LDH A₄ and AC hybrid were increased in brain tissue. The LDH activities in tissues from C. auratus and L. macrochirus remained 30.30-18.64% and 25-18.75%, respectively, as a result of the inhibition by 10 mM of pyruvate. The Km^PYR values of LDH in C. auratus were increased. As a result, LDH liver-specific C₄ isozyme was expressed in liver, brain and eye tissues during starvation. It seems metabolism of lactate was predominant in brain tissue. After starvation, the liver-specific LDH-C was affected more than eye-specific LDH-C.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.1
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• pp.73-78
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• 1994

This experiment was carried out to investigate the major characteristics associated with the flavor rate and their changes according to days after silking of super sweet corn(Cocktail 86) for vegetable and waxy corn(Chalok 1). Ear elongation finished around 22∼24 days after silking. In kernel development, elongation was much more prominant in super sweet corn than that in waxy corn but thickness was vice versa. Pericarp thickness and kernel hardness of super sweet corn were slightly increased but those of waxy corn were increased rapidly as the ears matured. Moisture and sucrose content of super sweet corn remained high but the waxy corn was not. The reducing sugars(glucose, fructose) were relatively high at the early maturity stage but they were decreased as the ears matured and negatively correlated with sucrose and flavor rate. Soluble solids (Brix %) were positively correlated with sucrose and total sugar(sucrose+ glucose+fructose) content in waxy corn but not in super sweet corn and was considered as inappropriate criate criterion to envaluate the sugar content and flavor rate. Pericarp thickness and sucrose content were positively correlated with the flavor rate in both hybrids but total sugar content, and kernel hardness were positively correlated with flavor rate in super sweet corn and waxy corn respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.98-102
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• 1995

Popped popcorn generally have a regular popping direction and typical shape. But the reason and mechanism are not clear yet. This experiment was carried out to investigate the shape moulding factor of popped popcorn. Pericarp thickness of tip-cap section of kernels is slightly thicker than that of top section and this fact provides the important information to the reason. Popping starts when the moisture pressure of heated popcorn is increased and reaches at the critical pressure. Therefore, in the same moisture pressure conditions, top sections are bursted first because their pericarp section is thinner than that of tip-cap section. At the very moment tip-cap sections pull down the top sections of peri carp as bi-metal does. So kernels which removed tip-cap section showed the irregular popping shape because they lost the tip-cap pericarp function. How-ever, kernels which removed embryo showed the typical popping shape but their popping volume was small due to emition and shortage of critical moisture pressure. But kernels which removed the whole pericarp and top pericarp were not popped at all because moisture was entirely emitting out of kernels. These results suggest that the shape moulding factor of popped popcorn is the pericarp thickness differences between the top and tip-cap section of kernels.

• Journal of Life Science
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• v.28 no.3
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• pp.351-356
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• 2018

L-Serine dehydratase (LSD) is an iron-sulfur containing enzyme that catalyzes the conversion of L-serine to pyruvate and ammonia. Among the bacterial amino acid dehydratases, it appears that only the L-serine specific enzymes utilize an iron-sulfur cluster at their catalytic site. Moreover, bacterial LSDs are classified into four types based on structural characteristics and domain arrangement. To date, only the LSD enzymes from a few bacterial strains have been studied, but more detailed investigations are required to understand the catalytic mechanism of various bacterial LSDs. In this study, LSD type II from Mycobacterium tuberculosis (MtLSD) H37Rv was expressed and purified to elucidate the biochemical and catalytic properties using the enzyme kinetic method. The L-serine saturation curve of MtLSD exhibited a typically sigmoid character, indicating an allosteric cooperativity. The values of $K_m$ and $k_{cat}$ were estimated to be $59.35{\pm}1.23mM$ and $18.12{\pm}0.20s^{-1}$, respectively. Moreover, the plot of initial velocity versus D-serine concentration at fixed L-serine concentrations showed a non-linear hyperbola decay shape and exhibited a competitive inhibition for D-serine with an apparent $K_i$ value of $30.46{\pm}5.93mM$ and with no change in the $k_{cat}$ value. These results provide insightful biochemical information regarding the catalytic properties and the substrate specificity of MtLSD.

• Journal of Life Science
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• v.19 no.2
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• pp.256-263
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• 2009

The lactate dehydrogenase (EC 1.1.1.27, LDH) $A_4$ isozyme in skeletal muscle of mandrin fish (Siniperca scherzeri) was successfully purified by affinity chromatography and ultrafiltration. The molecular weight of the purified LDH $A_4$ isozyme was 140.4 kDa and its isoelectric point (pI) was 7.0. Optimal pH for enzymatic reaction was 7.5. ${K_m}^{PYR}$ and $V_{max}$ value of the purified LDH $A_4$ isozyme were $4.86{\times}10^{-5}$ M and 13.31 mM/min using pyruvate as a substrate, respectively. These kinetic properties of the purified LDH $A_4$ isozyme supported the fact that the mandrin fish was a warm-adapted species. The antibody against the purified LDH $A_4$ isozyme may be used in the metabolic physiological studies of ectothermic vertebrates and in the diagnosis of several human diseases.

• Journal of Life Science
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• v.14 no.4
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• pp.708-715
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• 2004

The lactate dehydrogenase (EC 1.1.1.27, LDH) in liver of Lempetra japonica was purified in buffer of affinity chromatography. The liver-specific $C_4$ isozyme of Gadus macrocephalus was purified by heat treatment, affinity chromatography, and DEAE-Sephacel chromatography. The liver-specific $C_4$ isozyme was eluted in a buffer containing NAD+ and was coeluted with $B_4$isozyme in plain buffer of affinity chromagraphy. Liver-specific $C_4$ isozyme in G. macrocephalus was the most thermostable, and$B_4$isozyme was more stable than $A_4$. The LDH in the fraction of pH 7.45 purified from the liver of L. iaponica by chromatofocusing was more inhibited by pyruvate than purified LDH. The optimum pH of the LDH isozyme in the liver of L. japonica was 7.5 and that of liver-specific$C_4$ isozyme was 8.5. The LDH in liver of L. japonica made complexes more with antibody against Coreoperca herzi$A_4$ and liver-specific $C_4$ than with that against eye-specific $C_4$. Therefore, the structure of the LDH in liver of L. japonica might be similarly evolved to that of subunit A and liver-specific $C_4$ isozyme in liver tissue of G. macrocephalus. The evolution rate of subunit C is faster than that of subunit A. LDH in liver of L. japonica has not one isozyme but isozymes and it was also found out to have not only subunit A and B but also subunit C.

• Korean Journal of Food Science and Technology
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• v.18 no.1
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• pp.71-76
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• 1986

Changes in pH, titratable acidity, some organic acids and brix of the strawberry stored at the different levels of $CO_2$, in air were measured. The changing trends in pH and the acidity of the strawberries were not clear among the storage treatments, and pH of the strawberries in all the treatments was increased(r=0.9615) by contrast to decrease in the acidity(r=-0.8483). Ascorbic acid content of the strawberries at control lot was higher than the contents of the CA stored for the initial 2 weeks after storage. This trend was reversed after that period and the strawberries in air with 30% $CO_2$, showed the highest retention rate, 28% of the initial content after 5 weeks. Among the analyzed organic acids, malic acid was gradually decreased in all the treatments during storage and the decreasing rates of the strawberries in air with 30% $CO_2$, was somewhat stupider than those in the others. Pyruvic acid was reduced in the control lot during storage but drastically increased in the strawberries stored at the CA storage conditions between the 2nd and the 3rd week after storage, and then it was decreased.