• Journal of Microbiology and Biotechnology
• /
• v.17 no.9
• /
• pp.1579-1584
• /
• 2007

5-Aminolevulinate (ALA) synthase (E.C. 2.3.1.37), which mediates the pyridoxal phosphate-dependent condensation of glycine and succinyl-CoA, encoded by the Rhodobacter sphaeroides hemA gene, enables Escherichia coli strains to produce ALA at a low level. To study the effect of the enhanced C4 metabolism of E. coli on ALA biosynthesis, NADP-dependent malic enzyme (maeB, E.C. 1.1.1.40) was coexpressed with ALA synthase in E. coli. The concentration of ALA was two times greater in cells coexpressing maeB and hemA than in cells expressing hemA alone under anaerobic conditions with medium containing glucose and glycine. Enhanced ALA synthase activity via coupled expression of hemA and maeB may lead to metabolic engineering of E. coli capable of large-scale ALA production.

• Molecules and Cells
• /
• v.39 no.5
• /
• pp.426-438
• /
• 2016

Plant disease resistance occurs as a hypersensitive response (HR) at the site of attempted pathogen invasion. This specific event is initiated in response to recognition of pathogen-associated molecular pattern (PAMP) and subsequent PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). Both PTI and ETI mechanisms are tightly connected with reactive oxygen species (ROS) production and disease resistance that involves distinct biphasic ROS production as one of its pivotal plant immune responses. This unique oxidative burst is strongly dependent on the resistant cultivars because a monophasic ROS burst is a hallmark of the susceptible cultivars. However, the cause of the differential ROS burst remains unknown. In the study here, we revealed the plausible underlying mechanism of the differential ROS burst through functional understanding of the Magnaporthe oryzae (M. oryzae) AVR effector, AVR-Pii. We performed yeast two-hybrid (Y2H) screening using AVR-Pii as bait and isolated rice NADP-malic enzyme2 (Os-NADP-ME2) as the rice target protein. To our surprise, deletion of the rice Os-NADP-ME2 gene in a resistant rice cultivar disrupted innate immunity against the rice blast fungus. Malic enzyme activity and inhibition studies demonstrated that AVR-Pii proteins specifically inhibit in vitro NADP-ME activity. Overall, we demonstrate that rice blast fungus, M. oryzae attenuates the host ROS burst via AVR-Pii-mediated inhibition of Os-NADP-ME2, which is indispensable in ROS metabolism for the innate immunity of rice. This characterization of the regulation of the host oxidative burst will help to elucidate how the products of AVR genes function associated with virulence of the pathogen.

• Food Science and Preservation
• /
• v.18 no.5
• /
• pp.795-802
• /
• 2011

To determine the deacidification factor during carbonic maceration (CM), different temperature conditions were studied. The pH was higher in CM-$35^{\circ}C$ and CM-$25^{\circ}C$ and was lower in CM-$45^{\circ}C$. The total acid was inversely related to the pH. The malic-acid level decreased much more in CM-$35^{\circ}C$ than in CM-$45^{\circ}C$ while the lactic-acid level increased much more in CM-$35^{\circ}C$. The activity of the NADP-malic enzyme, which catalyzes the oxidative decarboxylation of L-malate into pyruvate, $CO_2$, and NADPH, was higher in CM-$25^{\circ}C$ and CM-$35^{\circ}C$ while CM-$45^{\circ}C$ showed no NADP-malic enzyme activity. The malic-dehydrogenase (MDH) activity was higher in CM-$25^{\circ}C$ and CM-$35^{\circ}C$ while CM-$45^{\circ}C$ showed no MDH activity. The oxalacetate decarboxylase activity was similar to the NADP-malic-enzyme and MDH activities. Pyruvate decarboxylase activity was shown in all the CM treatments. The L-lactic dehydrogenase (LDH) activity was not explored in the fermentation of pyruvate to lactate via LDH in the grapes during CM. In this study, it was confirmed that carbonic maceration reduced the malic acid during fermentation and was affected by the temperature. Moreover, it was assumed that the deacidification during the carbonic maceration of the grapes was probably correlated with the degradation enzyme activity of malic acid.

• Preventive Nutrition and Food Science
• /
• v.4 no.1
• /
• pp.79-83
• /
• 1999

A potentiometric biosensor employing a CO3-2 ion-selective electrode(ISE) and malic enzyme immobilization in al flow injection analysis (FIA) system was constructed. Analytical parameters were optimized for L-malate determination . The CO3-2 -ISE-FIA system was composed of a pump, an injector, a malic enzyme (EC1.1.1.40) reactor, a CO3-2 ion-selective electrode, a pH/mV meter and a recorder. Cofactor NADP was also injected with substrate for theenzyme reaction into the system. Optimized analytical parameters for L-malate determination in the CO3-2 ISE-FIA system were as follows ; flow rate, 14.5ml/hr ; sample injection volume, 100ul; enzyme loading in the reactor, 20 units ; length of the enzyme reactor , 7 cm ; tubing length form the enzyme reactor to the detector as a geometric factor in FIA, 15 cm . The response time for measuring the entire L-malate concentration range (10-2 ~10-5 mol/L ; 4 injections )was <15minutes . In this CO3-2 -ISE-FIA system, the potential differences due to th eformation of CO3-2 by the reaction of malic enzyme on L-malate were correlated to L-malate concentration in the range of 10-2 ~10-5mol/L ; the detection limit was 10-5 mol/L. This potentionmetric CO3-2 ISE--FIA system was found to be useful for L-malate measurement.

• Korean Journal of Weed Science
• /
• v.8 no.2
• /
• pp.133-140
• /
• 1988

One hundred and one noxious weeds on cultivated land of Taiwan were investigated for the occurrence of "Kranz" leaf anatomy and activities of PEP carboxylase and $C_4$ acid decarboxylating enzymes : NADP-malic enzyme, NAD-malic enzyme, PEP carboxykinase. Based on the leaf anatomy and a/b chlorophyll ratio, twenty-seven species exhibit "Kranz" type leaf anatomy, and seventy-four species were found without it. Among the species investigated, Digitaria radicosa (Presl) Miq., Leptochloa chinensis (L.) Nees, and Sporobolus fertilis (Steud.) W. D. Clayton in the Gramineae were first recorded as $C_4$ plants. Twenty-sven species of "Kranz" type leaf anatomy, include those of monocotyledon ; sixteen species in Gramineae, six species in Cyperaceae. Those of dicotyledon ; two species each in Euphorbiaceae and Amaranthaceae and one species in Portulacaceae. The subtype of fourteen previously uninvestigated species among twenty-seven species were further determined. The properties of the three decarboxylating enzyme from representative species were also characterized.

• Asian-Australasian Journal of Animal Sciences
• /
• v.16 no.3
• /
• pp.403-408
• /
• 2003

The study investigated the lipid metabolism of Tsaiya ducks under fasting and ad libitum feeding conditions. Sixty Tsaiya ducks in their growing period (8-12 wk-old) and sixty Tsaiya ducks in their laying period (26-30 wk-old, 10-14 weeks after the onset of laying) were randomly divided into ad libitum feeding and 3-day fasting groups. The activities of lipid metabolism related enzymes were determined. Experimental results indicated that fasting depressed the activities of lipogenesis related enzymes such as fatty acid synthetase and NADP-malic dehydrogenase in both periods (p<0.05). Fasting also increased the activities of liver fatty acid $\beta$-oxidation enzymes (p<0.05). However, the activities of lipoprotein lipase in adipose tissue, heart and ovarian follicle in both periods and the hormone-sensitive lipase of adipose tissue in the growing period were decreased by fasting (p<0.01).

• Journal of Microbiology and Biotechnology
• /
• v.23 no.5
• /
• pp.668-673
• /
• 2013

A recombinant E. coli co-expressing ALA synthase (hemA), NADP-dependent malic enzyme (maeB), and dicarboxylic acid transporter (dctA) was reported to synthesize porphyrin derivatives including iron-containing heme. To enhance the synthesis of bacterial heme, five genes of the porphyrin biosynthetic pathway [pantothenate kinase (coaA), ALA dehydratase (hemB), 1-hydroxymethylbilane synthase (hemC), uroporphyrinogen III synthase (hemD), and uroporphyrinogen III decarboxylase (hemE)] were amplified in the recombinant E. coli co-expressing hemA-maeB-dctA. Pantothenate kinase expression enabled the recombinant E. coli to accumulate intracellular CoA. Intracellular ALA was the most enhanced by uroporphyrinogen III synthase expression, porphobilinogen was the most enhanced by ALA dehydratase expression, uroporphyrin and coproporphyrin were the most enhanced by 1-hydroxymethylbilane synthase expression. The strain co-expressing coaA, hemA, maeB, and dctA produced heme of $0.49{\mu}mol/g$-DCW, which was twice as much from the strain without coaA expression. Further pathway gene amplifications for the porphyrin derivatives are discussed based on the results.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.6
• /
• pp.604-609
• /
• 2009

To investigate the potential use of microbial heme as an iron source, recombinant Escherichia coli coexpressing ALA synthase (HemA) as well as the NADP-dependent malic enzyme (MaeB) and dicarboxylic acid transporter (DctA) were cultured. The typical red pigment extracted from the recombinant E. coli after 38 h showed highest absorbance at 407 nm, and the amount of iron in 38.4 mg of microbial heme extract derived from 6-1 fermentation broth was 4.1 mg. To determine the commercial potential of the recombinant E.coli-synthesized iron-associated heme as an iron source, mice were fed the iron-free provender with the microbial heme extract. The average body weight reduction of mice fed non-iron provender was 2.3%, whereas no detectable weight loss was evident in mice fed microbial heme addition after 15 days. The heme content of the blood from microbial heme fed mice was 4.2 mg/ml whereas that of controls was 2.4 mg/ml, which implies that the microbial heme could be available for use as an animal iron source.

• Asian-Australasian Journal of Animal Sciences
• /
• v.18 no.2
• /
• pp.241-248
• /
• 2005

This study is aimed at understanding the role of arsenic in Roxarsone in causing fatty livers in mule ducks. One hundred 10-week-old mule ducks were randomly divided into 5 groups. Ducks received 2 weeks of various treatments followed by 2 weeks of withdrawal. The treatments were non-treatment (control), 300 mg/kg Roxarsone inclusion for 2 weeks ($1^{st}$ and $2^{nd}$ week), Roxarsone inclusion for one week ($2^{nd}$ week only), restrict feeding, or Roxarsone analogue (3-nitro-4-hydroxyphenyl acid) inclusion. Results showed that feed intake and body weight in the Roxarsone groups and the restrict feeding group decreased significantly during the treatment period. However only the liver and heart weights were significantly decreased (p<0.05) in the restrict feeding group. Fatty acid synthetase (FAS) activity showed a significant decrease (p<0.05) in the Roxarsone groups and the restrict feeding group, two-week-Roxarsone treatment significantly increased NADP-malic dehydrogenase (MDH) activity compared to the restrict (p<0.05). After 2 weeks drug withdrawal, the 1-week-Roxarsone or restrict feeding group showed significantly increased (p<0.05) glucose-6-phosphate dehydrogenase (G-6-PDH) activity (p<0.05). Two-week-Roxarsone treatment significantly decreased (p<0.05) the high density lipoprotein (HDL) and increased (p<0.05) the low density lipoprotein (LDL) and very low density lipoprotein (VLDL) ratio. After drug withdrawal, the 1-week-Roxarsone or restrict feeding group showed significantly increased (p<0.05) creatine kinase (CK) activity. The 2-week-Roxarsone treatment group showed significantly increased (p<0.05) aspartate aminotransferase (AST) activity. The restrict feeding treatment group showed significantly decreased (p<0.05) total protein (TP) concentration. After drug withdrawal, the related enzyme activities in the blood that reflected the liver function were restored to the normal physiological range, except for the total bilirubin concentration and CK activity in the 1-week-Roxarsone group. This group showed a significant increase (p<0.05). Thus, the reasons for liver enlargement in the Roxarsone and restrict feeding groups were different.

• Asian-Australasian Journal of Animal Sciences
• /
• v.19 no.3
• /
• pp.438-443
• /
• 2006

This trial was designed to study the caponization effects on the appearance, carcass characteristics, blood constituents and lipid metabolism of Taiwan country chicken cockerels. Cockerels were caponized at 8 weeks of age. Sixteen-week-old chickens, including 10 capons, 5 slips (incomplete caponized male chickens) and 20 normal chickens of equal sexes were selected for a 10 week ad libitum feeding trial. Results showed that the testosterone concentrations in the capons and females were lower (p<0.05) than that of intact males. The comb length, height and weights were also lower (p<0.05). The weight of the slips was between that of the capons and intact males, but was heavier (p<0.05) than that of the capon. The live-weight, carcass weight and shank perimeter in the capons were higher than those of the other groups (p<0.05). Hepatic lipogenic enzyme activity analyses showed that NADP-malic dehydrogenase (MDH) activity in the capons and female chickens was higher than that in intact male chickens (p<0.05). The MDH activity in the slips was between that for the capon and intact male chickens (p>0.05). The abdominal fat weight and relative abdominal fat weight of the capons and females were heavier than that for intact males (p<0.05); the slips were between the capons and intact males. The blood lipid content results showed that the triacylglycerol and cholesterol in the capons were higher than that for intact males (p<0.05). However, the percentage of low-density lipoprotein (LDL) was lower than that in intact male chickens (p<0.05). It appears that the increase in lipid accumulation in caponized male chickens is attributed mainly to an increase in MDH activity and the changes in lipid transportation in the capons.