• Bulletin of the Korean Chemical Society
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• 제18권4호
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• pp.428-432
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• 1997

The dephosphorylation specificity of protein phosphatase 2A (PP2A), calcineurin (PP2B) and protein phosphatase 2C (PP2C) were studied in vitro using myelin basic protein (MBP) as a model substrate which was fully phosphorylated at multiple sites by protein kinase C (PKC) or cyclic AMP-dependent protein kinase (PKA). In order to determine the site specificity of phosphates in myelin basic protein, the protein was digested with trypsin and the radioactive phosphopeptide fragments were isolated by high performance liquid chromatography (HPLC) on reversed-phase column. Subsequent analysis and/or sequential manual Edman degradation of the purified phosphopeptides revealed that Thr-65 and Ser-115 were most extensively phophorylated by PKA and Ser-55 by PKC. For the dephosphorylation kinetics, the phosphorylated MBP was treated with calcineurin or PP2C with various time intervals and the reaction was terminated by direct tryptic digest. Both Thr-65 and Ser-115 residues were dephosphorylated more rapidly than any other ones by phosphatases. However it can be differentiated further by first-order kinetics that the PP2B dephosphorylated both Thr-65 and Ser-115 with almost same manner, whereas PP2C dephosphorylated somewhat preferentially the Ser-115.

• Natural Product Sciences
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• 제12권4호
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• pp.205-209
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• 2006

The structures of flavonoids, 2(S)-5,7-dihydroxy-8,2'-dimethoxyflavanone (1), wogonin (2), 2(S)-5,7, 2'-trihydroxy-8-methoxyflavanone (3), and 2(S)-5,2',5'-trihydroxy-7,8-dimethoxyflavanone (4), isolated from Scutellaria indica were revised on the basis of 2D NMR spectroscopy, including to gCOSY, gHSQC, and gHMBC. Compounds 1-4 were tested in vitro protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. Compounds 2 and 4 exhibited weak PTP1B inhibitory activity with $IC_{50}$ values of 208 and $337{\mu}M$, respectively.

• 한국동물학회지
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• 제39권4호
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• pp.426-436
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• 1996

앞서 본 연구실에서는 도롱뇽(Hynobius leechii) 다리 재생 과정중 기존의 조직들이 와해되고 조직 및 그 구성 세포의 분화 양성이 소멸되는 탈분화 과정중 시소솜 acid phosphatase의 활성도가 급격히 증가함을 보고한바 있다. 본 연구에서는 다리 재생 과정에서 이 효소의 시간적, 공간적 분포 및 발현 양상을 알아보기 위해 단일 항체를 만들었다. 리소솜 acid phosphatase에 대한 22단일 항체균중 5항체군이 탈분화 조직과 강한 면역반응을 보였으며 이들의 시간적, 공간적 반응 양상은 조직의 탈분화 상태와 일치하였다. 이 결과는 탈분화 과정시 증가하는 리소솜 acid phosphatase의 활성도가 이 효소의 시간적, 공간적 분포 및 발현 양상과 밀접히 연관되어 있음을 반영하며 탈분화 과정중 이 효소의 역할이 매우 중요함을 시사하고 있다. Immunoblotting 결과 이들 단일 항체군은 리소솜 acid phosphatase의 monomer인 53kDa밴드를 인식하였다. 한편 도롱뇽의 리소솜 acid phosphatase에 대한 단일 항체와 타종의 LAP에 대한 cross-reactivity를 immunoblot으로 조사한 결과 양서류인 axolotl(Ambystoma mexicanum)과 Xenopus laevis에서는 유사한 분자량 band에서 반응이 나타났으나 그외 생쥐, 초파리, C.elegans에서는 cross-reactivity가 없는 것으로 조사되었다. 이러한 결과들은 본 연구에서 만들어진 단일 항체가 한국산 도롱뇽의 리소솜 acid phosphatase를 특이적으로 인식하며 나아가 양서류내에서는 이 효소의 상동서이 높음을 시사하고 있다.

• Molecules and Cells
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• 제38권8호
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• pp.697-704
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• 2015

Deleted in breast cancer-1 (DBC1) contributes to the regulation of cell survival and apoptosis. Recent studies demonstrated that DBC is phosphorylated at Thr454 by ATM/ATR kinases in response to DNA damage, which is a critical event for p53 activation and apoptosis. However, how DBC1 phosphorylation is regulated has not been studied. Here we show that protein phosphatase 4 (PP4) dephosphorylates DBC1, regulating its role in DNA damage response. PP4R2, a regulatory subunit of PP4, mediates the interaction between DBC1 and PP4C, a catalytic subunit. PP4C efficiently dephosphorylates pThr454 on DBC1 in vitro, and the depletion of PP4C/PP4R2 in cells alters the kinetics of DBC1 phosphorylation and p53 activation, and increases apoptosis in response to DNA damage, which are compatible with the expression of the phosphomimetic DBC-1 mutant (T454E). These suggest that the PP4-mediated dephosphorylation of DBC1 is necessary for efficient damage responses in cells.

• BMB Reports
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• 제28권4호
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• pp.331-335
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• 1995

Simian virus 40 (SV40) small-t antigen (small-t) has been known to regulate the activity of a cellular enzyme, protein phosphatase 2A (PP2A), composed of A. B, and C subunits, via binding to the A subunit In the study presented here, the stoichiometry of the binding of small-t to PP2A was determined to be 1: 1. It was also shown that small-t binds to the AC form of PP2A with a higher apparent affinity than it binds to the free A subunit. We also characterized the interaction of PP2A with wild-type and various mutant small-ts. A single-point mutant (Val134Met) and a double-point mutant (Trp147Gly;Leu152 Pro) of small-t exhibited 3-fold and 5-fold lower potencies in inhibiting PP2A activity. respectively. This suggests that the region around amino acids between 134 and 152 of small-t might be important in regulating the enzyme activity of PP2A.

• 한국식품영양과학회지
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• 제27권4호
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• pp.724-730
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• 1998

Effects of raw soy flour(RSY) and black(RSB) feeding on protein concentration of liver and serum, and GOT, GPT and alkaline phosphatase activities of serum in diabetic and nondiabetic rats were studied. Male rats(Sprague-Dawley), mean weight of (338.4$\pm$19.2g) were assigned to six dietary groups and fed with the assigned diet for 28 days. For each experimental, some rats were injected with streptozotocin intraperitoneally(L.P.) to induce diabets, and other rats were injected with buffer L.P. as a control group. The liver, kidney and spleen weights relative to bo요 weigth were higher in raw yellow soy flour diet diabetes(D-RSY) and black soy flour diet diabetes(D-RSB) groups than control, but the body weights were lower than control. The protein and albumin concentrations of liver and serum were lower in D-RSY and D-RSB groups than control. The albumin concentration of serum in D-RSB group was lower than control. The GOT activities of serum in RSY and RSB groups were increased compared with control, but the GPT activities were lower in diabetic control, D-RSY and D-RSB groups than control. The alkaline phosphatase activities of serum in RSY and RSB groups were higher than control, but those in D-RSY and D-RSB groups were lower than diabetic control.

• 생명과학회지
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• 제24권1호
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• pp.14-19
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• 2014

Kinesin-1은 2개의 장쇄(KHCs, 또는 KIF5s)와 2개의 단쇄(KLCs)가 결합한 복합체로 되어 있다. 본 연구에서 효모 two-hybrid system을 이용하여 중추신경계의 신경세포에서 주로 발현되는 KIF5A와 결합하는 단백질을 탐색한 결과 phosphatidylinositol-3,5-bisphosphate ($PI(3,5)P_2$)의 5번 위치 인산을 제거하는 탈인산화효소 Fig4(Sac3)를 분리하였다. KIF5A는 Fig4의 C-말단과 결합함을 효모 two-hybrid assay로 확인하였다. Fig4는 KIF5A의 C-말단과 결합하지만, 두 개의 다른 장쇄인 KIF5B와 KIF5C 그리고 KLC1와는 결합하지 않았다. 단백질 간 결합을 glutathione S-transferase pull-down assay와 공동면역침강으로 추가 검증하였다. 생쥐의 뇌 파쇄액을 KIF5A 항체로 면역 침강한 결과 Fig4가 같이 침강하였다. 이러한 결과들은 kinesin-1이 Fig4와 결합한 단백질 복합체 혹은 운반체를 세포 내에서 운반함을 시사한다.

• Natural Product Sciences
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• 제16권4호
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• pp.239-244
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• 2010

Protein tyrosine phosphatase 1B (PTP1B), a negative regulator of insulin signaling, has served as a potential drug target for the treatment of type 2 diabetes. The MeOH extracts of twenty-nine medicinal plants, traditionally used in Vietnam as anti-diabetes agents, were investigated for PTP1B inhibitory activity in vitro. The results indicated that, most materials showed moderate to strong inhibitory activity with $IC_{50}$ values ranging from $3.4\;{\mu}g/mL$ to $35.1\;{\mu}g/mL$; meanwhile, eleven extracts (37.9%) could demonstrate PTP1B activity with $IC_{50}$ values less than $15.5\;{\mu}g/mL$; sixteen extracts (55.2%) could demonstrate PTP1B activity with $IC_{50}$ values ranging from $15.5\;{\mu}g/mL$ to $35.1\;{\mu}g/mL$. The study may provide a proof, at least in a part, for the ethno-medical use in diabetes disease of these plants.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3772-3776
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• 2012

Mitogen-activated protein kinase phosphatase 4 (MKP4) has proved to be a promising target for the development of therapeutics for the treatment of diabetes and the other metabolic diseases. Here, we report an example for a successful application of the structure-based virtual screening to identify three novel inhibitors of MKP4. These inhibitors have desirable physicochemical properties as a drug candidate and reveal a moderate potency with $IC_{50}$ values ranging from 4.9 to $32.3{\mu}M$. Therefore, they deserve consideration for further development by structure-activity relationship studies to optimize the inhibitory and antidiabetic activities. Structural features relevant to the stabilization of the newly identified inhibitors in the active site of MKP4 are discussed in detail.

• 대한지역사회영양학회지
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• 제4권2호
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• pp.239-247
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• 1999

Six-week-old Sprague Dawley rats were fed the diets of 20% casein or soy protein. Two weeks after the feeding, hepatocellular chemical carcinogenesis was initiated by diethylnitrosamine(DEN), and promoted by the diet containing 0.01% 2-acetylamino-fluorene(AAF) and two-thirds partial hepatectomy(PH). The animals were sacrificed at 8 weeks after the DEN injection. The area of placetal glutathione S-trnasferase(GST-P) positive foci, the activities of several enzymes in cellualr antioxidant enzyme systems and glucose 6-phosphatase were determined to investigate the mechanism of the anticarcinogenic effect by the dietary proteins. In another set of experiments, the drinking water of rats fed casein was supplemented with 1.5% inositol hexaphosphate(InsP6) to elucidate whether it has the comparable anticancer action of soy protein. The area and number of GST-P positive foci in the soy protein group were significantly(p<0.05) lower than those inthe casein group. The livers of rats fed casein showed moderate fattydegeneration and larger hyperplastic nodules than those of rats fed soy protein. In another set of experiments, the area and number of GST-P positive foci in the rats fed casein supplemented with InsP6 were not significantly different from those in the rats fed casein or soy protein. The lipid peroxidation of rats fed different protein sources showed no significant difference. Glutathione S-transferase(GST) activities were increased significantly(p<0.05) by carcinogen treatment in all dietary groups. Glucose 6-phosphatase(G6Pase) activities were decreased by carcinogen treatment, and hence showed a reverse relationship(r=-0.695, p<0.01) to the GST-P positive foci. Therefore, the activities in the rats fed casein were lower than those in the rats fed soy protein. These results suggest that the soy protein seems to be more anti-carcinogenic than casein by decreasing the preneoplastic lesion and by increasing the membrane stability but inositol hexaphosphate, a component of soy protein, may not be protective against hepatocarcinogenesis.