• 한국식품과학회지
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• 제21권1호
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• pp.120-126
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• 1989

Str. diacetylactis와 Leu. cremoris를 commercial culture로부터 분리한 후 멸균된 10%(w/v) 환원 탈지유에 단독 및 혼합(1 : 1) 배양하면서 diacetyl 생성에 미치는 배양 조건에 대하여 검토하였다. 생육최적 온도는 Str. diacetylactis의 경우 $30^{\circ}C$, Leu, cremoris는 $34^{circ}C$로 나타났으나, diacetyl 생성 최적 온도는 모두 $22^{\circ}C$로, 2%(v/v) starter 접종시 Str. diacetylactis, Leu. cremoris 그리고 혼합 배양의 경우 diacetyl 생성량은 각각 배양 60, 48, 48시간에 2.24, 2.29, 2.21ppm으로 최대치를 보인 후 감소하는 경향을 나타내었다. 배지내 초기 pH는 pH 4.8에 모두 최고의 diacetyl 생성량을 보여 각각 4.32, 6.66, 7.30ppm을 나타내었다. Starter 접종량이 많아질수록 diacetyl 생성량은 증가하였지만 증가폭은 크지 않았으며 diacetyl의 전구 물질인 citrate를 sodium citrate형태로 농도별로 첨가하였을 때 0.3, 0.1, 0.1%(w/v) 첨가시에 각각 2.58, 2.54, 2.52ppm으로 최대치를 보였다. 최적 조건하에서 24시간 배양시 diacetyl 생성량은 각각 4.40, 6.59, 7.25ppm으로 나타났으며, diacetyl생성에 가장 큰 영향을 미치는 것은 초기 pH인 것으로 밝혀졌다.

• 한국수산과학회지
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• 제20권5호
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• pp.431-440
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• 1987

Papain, pepsin, $\alpha-chymotrypsin$ 및 protease을 이용하여 말쥐치육 단백질의 pepsin가수분해물로 부터 합성한 plastein과 유리 glutamic acid 및 leucine을 도입시킨 plastein의 일반성분, 아미노산조성, 분자량, 색조 및 IR spectrum을 측정하여 비교 검토한 결과를 요약하면 다음과 같다. Plastein의 단백질함량은 $76.4\~79.0\%$였으나 protease plastein만이 $72.4\%$로 다소 낮았으며, 회분함량은 $7.4\~11.8\%$로 Glu-papain plastein과 Leu-papain plastein의 $3.9\%$ 및 $4.1\%$보다 높았고, 지방 함량은 $0.3\~0.9\%$ 범위였다. 수율은 papain plastein이 $55\%$로 가장 높았고, pepsin plastein, $\alpha-chymotrypsin$ 및 pretense plastein은 각각 $47.6\%,\;38.3\%,\;23.6\%$ 였으며, Glu-papain plastein과 Leu-papain plastein은 각각 $35.0\%,\;45.7\%$ 였다. Plastein 종류에 따른 아미노산조성에는 큰 차이는 없었으며, Glu-papain plastein과 Leu-papain plastein의 glutamic acid 및 leucine함량은 각각 $38.7\%,\;41.7\%$였으나 대조구인 papain plastein에서는 이들의 함량이 $14.0\%,\;10.1\%$에 불과하였다. Gel여과법에 의한 가수분해물의 분자량은 2,000 및 310인 것이 주종을 이루었으나 이외에도 분자량이 1,600 및 120인 획분도 존재하였다. Plastein의 분자량은 papain plastein이 21,000 및 4,900 였으며, pepsin plastein 24,000, $\alpha-chymotrypsin$ plastein 18, 500, protease plastein 6,700, Glu-papain plastein 24,000, Leu-papain plastein은 17,000 이었다. IR spectrum상에서는 동결건조육, FPC및 가수분해물간에 거의 차이가 없었다.. 그러나 plastein의 경우는 이들과 달리 $800\~850\;cm^{-1},\;700\~750\;cm^{-1} 및 $600\~700\;cm^{-1}$에서 강한 흡수띠가 나타났지만 protease plastein만이 흡수띠가 비교적 약하였다. Glu-papain plastein은 amide I의 흡수띠가 넓게 퍼진 반면에 $1,440cm^{-1}$에서 새로운 흡수띠가 나타났다. 그러나 Leu-papain plastein의 경우는 특징적인 흡수띠가 나타나지 않았다.

• Asian-Australasian Journal of Animal Sciences
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• 제32권6호
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• pp.842-848
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• 2019

Objective: Heat stress poses an increasing threat for poultry production. Some amino acids have been found to play critical roles in affording thermotolerance. Recently, it was found that in ovo administration of L-leucine (L-Leu) altered amino acid metabolism and afforded thermotolerance in heat-exposed broiler chicks. Methods: In this study, two doses (35 and $70{\mu}mol/egg$) of L-Leu were administered in ovo on embryonic day 7 to determine their effect on rectal temperature (RT), body weight (BW) and thyroid hormones at hatching. Changes in RT, BW, and thermotolerance in post-hatched chicks were also analyzed. Results: It was found that in ovo administration of L-Leu dose-dependently reduced RT and plasma thyroxine ($T_4$) level just after hatching. In post-hatched neonatal broiler chicks, however, the higher dose of L-Leu administered in ovo significantly increased RT without affecting BW gain. In chicks that had been exposed to heat stress, the RT was significantly lowered by in ovo administration of L-Leu (high dose) in comparison with the control chicks under the same high ambient temperature (HT: $35^{\circ}C{\pm}1^{\circ}C$, 120 min). Conclusion: In ovo administration of L-Leu in a high dose contributed to an increased daily body temperature and afforded thermotolerance under HT in neonatal broiler chicks.

• 한국미생물·생명공학회지
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• 제23권4호
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• pp.454-460
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• 1995

Acetylxylan esterase II was produced by Escherichia coli HB101 harboring the recombinant plasmid pKMG7 which contained the estII gene of Bacillus stearothermophilus. Optimal medium for the production of the acetylxylan esterase by E. coli HB101/pKMG7 was determined to contain 0.5% galactose, 1% yeast extract and 1% NaCl. The enzyme produced was purified to homogeneity using a combination of 20-50% ammonium sulfate precipitation, DEAE-Sepharose CL-6B chromatography and Sephacryl S-200 gel filtration. The temperature and pH optimum of the esterase were 45$\circ$C and pH 6, respectively. The essential amino acids for the esterase activity were found to be methionine, serine, and cysteine. Molecular weight of the esterase was determined to be 28 kDa by SDS-polyacrylamide gel electrophoresis, and 120 kDa by gel filtration. This suggests that the functional enzyme is a homomeric tetramer. The esterase had an isoelectric point of pH 3.4. The N-terminal amino acid sequence of the enzyme was Ala-Leu-Phe-Glu-Ser-Arg-Phe-Phe-Ser-Glu-Val-Leu-Gly-Leu.

• 한국식품과학회지
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• 제27권4호
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• pp.495-505
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• 1995

$5{\sim}7^{\circ}C$의 저온에서 20일 및 50일간 각각 발효된 A 및 B의 두 김치시료에서 저온성 젖산균 각각 30주씩을 무작위로 분리하고 동정을 하였다. 김치 A에서 분리한 30주 중 14주는 Leu. mesenteroides subsp. mesenteroides로, 12주는 Leu. mesenteroides subsp. dextranicum으로, 4주는 Lac. bavaricus로 각각 동정되었고, 김치 B에서 분리한 30주 중 20주는 Lac. bavaricus로, 3주는 Leu. mesenteroides subsp. mesenteroides로, 3주는 Leu. lactis로, 2주는 Leu. paramesenteroides로, 2주는 Lac. homohiochii로 각각 동정되었다. 비록 본 균주들이 위와 같이 동정되었지만 당류발효 pattern과 arginine에서 $NH_3$의 생성능이 Bergey's Manual of Systematic Bacteriology에 기재된 내용과 일치하지 않는 균주가 많았고, Leu. mesenteroides subsp. mesenteroides와 Leu. mesenteroides subsp. dextranicum으로 동정된 균주들 중의 일부는 당류발효 pattern이 동일 subspecies의 균주들 사이보다 다른 subspecies와 더욱 일치하는 모순까지 드러내었다. 이들 저온성 젖산균들을 기존의 체제에 따라 분류함에는 어려움이 따랐으며 이의 해결을 위한 후속연구가 요구되었다.

• 생명과학회지
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• 제8권4호
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• pp.395-399
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• 1998

Neurokinin A(NKA) and its derivatives ([Nle$^{7}$NKA,[Leu$^{7}$NKA] were synthesized by solid phase peptide synthesis method using Fmoc-TFA strategy and their smooth muscle contractile activities were measured to examine the structural effect of alkyl group at the 7th amino acid NKA on the smooth muscle contractile activity. The smooth muscle contractile activity. The smooth muscle contractile activities of [Nle$^{7}$]NKA and [Leu$^{7}$]NKA were only 5.64% and 1.55%, respectively when compared with NKA. This result suggested that the more three dimensional structure of th 7th amino acid as well as the whole message segment of NKA would be necessary to show the biological activity.

• KSBB Journal
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• 제9권2호
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• pp.191-199
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• 1994

김치 발효에 주관여 미생물로 작용하는 Lactoba-cillus plantarum, Leuconostoc mesenteroides 균주에 세포 융합법을 적용시켜 우수한 형질의 재조합체를 얻기 위한 균주 개량의 방법으로 이용하고자 하여 그 기초가 되는 원형질 형성의 최적 조건을 조사하였다. Protoplast를 생성하기 위하여 세포벽 용균 효소로 lysozyme $40{\mu}$g/ml와 protoplast 형성률이 가장 좋은 생육시기인 15hr으로 결정하였다. $30^{\circ}C$, pH 7.5에서 현저한 흡광도 감소 경향과 protoplast 형성률도 우수하였다. 15% sucrose, 20mM $MgCl_2$, 6mM $CaCl_2$에서는 흡광도 감소 경향을 보이지 않았으나 protoplast 형성률은 다른 농도에서보다 증가하는 경향을 나타냈다. Plasma expander로 알려진 gela tin을 첨가하였을 경우에는 660nm에서 유의적인 흡광도 감소 경향을 보이지 않았으며 단지 proto-plast를 형성시키는데 있어서 중요한 보조적 역할을 수행하는 것으로 여겨진다. 균주 발육을 하기 위한 최소 저지 농도를 조사한 결과 marker로 이용할 수 있는 항생제는 erythromycin($15{\mu}$g/ml), ampicillin($50{\mu}$/ml), tetracyclin($30{\mu}$g/ml), chloramphe-nicol($30{\mu}$g/ml)이었다. Leu. mesenteroides는 모든 조건에서 L.plantarum보다 용균 작용과 protoplast 형성 효율이 낮아 L. plantarum에 준하여 protoplast 생성조건을 결정하였다.

• 대한의생명과학회지
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• 제10권3호
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• pp.179-186
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• 2004

We examined a role of proteasome, the non-lysosomal multicatalytic protease complex,on the differentiation of chick embryonic myoblasts in culture. The peptide hydrolyzing activities of proteasome were found to change; the hydrolyzing activity against N-succinyl-Leu-Leu- Val- Tyr-7 -amido-4-methy1coumarin (SLLVY-AMC) was prominent and increased with myogenic differentiation. Proteasome inhibitors, N-carbobenzoxy-Leu-Leu-norvalinal (MG115) and N-carbobenzoxy-Ile-Glu (O-t-butyl)-Ala-Leucinal (PSI), blocked membrane fusion of myoblasts as well as the SLLVY-AMC hydrolyzing activity. Those inhibitory activities of the agents occurred in parallel, but were reversible and both cell fusion and the peptidase activity were restored when the agents were withdrawn from the culture medium. On the other hand, the agents caused accumulation of the ubiquitinylated proteins in the cytoskeletal proteins. These results suggest that each of the peptide hydrolyzing activities of proteasome is independently regulated during the myogenic differentiation and the chymotrypsin-like activity may play an important role in that process.

• Journal of Microbiology and Biotechnology
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• 제7권3호
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• pp.180-188
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• 1997

Bacillus subtilis C9 was selected by measuring the oil film-collapsing activity and produced biosurfactant in a medium containing glucose as a sole carbon source. The biosurfactant emulsified hydrocarbons, vegetable oils and crude oil, and lowered the surface tension of culture broth to 28 dyne/cm. A biosurfactant, C9-BS produced by B. subtilis C9 was purified by ultrafiltration, extraction with chloroform and methanol, adsorption chromatography, and preparative reversed phase HPLC. Structural analyses, IR spectroscopy, FAB mass spectroscopy, amino acid composition, and NMR analyses, demonstrated that C9-BS was a lipopeptide comprising a fatty acid tail and peptide moiety. The lipophilic part consisting of $C_{14}\;or\;C_{15}$ hydroxy fatty acid was linked to the hydrophilic peptide part, which contained seven amino acids (Glu-Leu-Leu-Val-Asp-Leu-Leu) with a lactone linkage.

• BMB Reports
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• 제35권2호
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• pp.228-235
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• 2002

Methionine aminopeptidase (MetAP) catalyzes the removal of an amino-terminal methionine from a newly synthesized polypeptide. The enzyme was purified to homogeneity from Bacillus stearothermophilus (KCTC 1752) by a procedure that involves heat precipitation and four sequential chromatographs (including DEAE-Sepharose ion exchange, hydroxylapatite, Ultrogel AcA 54 gel filtration, and Reactive red 120 dye affinity chromatography). The apparent molecular masses of the enzyme were 81,300 Da and 41,000 Da, as determined by gel filtration chromatography and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), respectively. This indicates that the enzyme is comprised of two identical subunits. The MetAP specifically hydrolyzed the N-terminal residue of Met-Ala-Ser that was used as a substrate, and exhibited a strong preference for Met-Ala-Ser over Leu-Gly-Gly, Leu-Ser-Phe, and Leu-Leu-Tyr. The enzyme has an optimal pH at 8.0, an optimal temperature at $80^{\circ}C$, and pI at 4.1. The enzyme was heat-stable, as its activity remained unaltered when incubated at $80^{\circ}C$ for 45 min. The Km and Vmax values of the enzyme were 3.0mM and 1.7 mmol/min/mg, respectively. The B. stearothernmophilus MetAP was completely inactivated by EDTA and required $Co^{2+}$ ion(s) for activation, suggesting the metal dependence of this enzyme.