scholarly journals Branched-chain-amino-acid-preferring peptidase activity of the lobster multicatalytic proteinase (proteasome) and the degradation of myofibrillar proteins

1995 ◽  
Vol 306 (1) ◽  
pp. 285-291 ◽  
Author(s):  
D L Mykles ◽  
M F Haire
Keyword(s):  
Amino Acid ◽  
Myofibrillar Proteins ◽  
Significant Finding ◽  
Peptidase Activity ◽  
Multicatalytic Proteinase ◽  
Branched Chain Amino Acid ◽  
Endogenous Protein ◽  
Proteolytic Activities ◽  
Branched Chain

The multicatalytic proteinase (MCP or proteasome) is a large proteolytic complex that contains at least five catalytic components: the trypsin-like, chymotrypsin-like, peptidylglutamyl-peptide hydrolase (PGPH), branched-chain-amino-acid-preferring (BrAAP) and small-neutral-amino-acid-preferring activities. We have shown that brief heating of the lobster muscle proteasome activates a proteolytic activity that degrades casein and myofibrillar proteins and is distinct from the trypsin-like, chymotrypsin-like and PGPH components. Here we identify the BrAAP activity as a catalytic component involved in the initial degradation of myofibrillar proteins in vitro. This conclusion is based on the following. (1) The BrAAP component was activated by heat-treatment, whereas the other four peptidase activities were not. (2) The BrAAP and proteolytic activities showed similar sensitivities to cations and protease inhibitors: both were inhibited by 3,4-dichloroisocoumarin, chymostatin, N-ethylmaleimide and Mg2+, but were not affected by leupeptin, phenylmethanesulphonyl fluoride or Li+. (3) The BrAAP activity was inhibited most strongly by casein substrates and troponin; conversely, the troponin-degrading activity was inhibited by the BrAAP substrate. Another significant finding was that incubation of the heat-activated MCP in the presence of chymostatin resulted in the limited cleavage of troponin-T2 (45 kDa) to two fragments of 41 and 42 kDa; this cleavage was completely suppressed by leupeptin. These results suggest that under certain conditions the trypsin-like component can cleave endogenous protein.

scholarly journals Branched-chain amino acid aminotransferase 2 regulates ferroptotic cell death in cancer cells

2020 ◽  
Author(s):  
Kang Wang ◽  
Zhengyang Zhang ◽  
Hsiang-i Tsai ◽  
Yanfang Liu ◽  
Jie Gao ◽  
...  
Keyword(s):  
Cell Death ◽  
Amino Acid ◽  
Cancer Cells ◽  
Ectopic Expression ◽  
Branched Chain Amino Acid ◽  
Pancreatic Cancer Cells ◽  
Key Enzyme ◽  
Branched Chain

Abstract Ferroptosis, a form of iron-dependent cell death driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated as a tumor-suppressor function for cancer therapy. Recent advance revealed that the sensitivity to ferroptosis is tightly linked to numerous biological processes, including metabolism of amino acid and the biosynthesis of glutathione. Here, by using a high-throughput CRISPR/Cas9-based genetic screen in HepG2 hepatocellular carcinoma cells to search for metabolic proteins inhibiting ferroptosis, we identified a branched-chain amino acid aminotransferase 2 (BCAT2) as a novel suppressor of ferroptosis. Mechanistically, ferroptosis inducers (erastin, sorafenib, and sulfasalazine) activated AMPK/SREBP1 signaling pathway through iron-dependent ferritinophagy, which in turn inhibited BCAT2 transcription. We further confirmed that BCAT2 as the key enzyme mediating the metabolism of sulfur amino acid, regulated intracellular glutamate level, whose activation by ectopic expression specifically antagonize system Xc– inhibition and protected liver and pancreatic cancer cells from ferroptosis in vitro and in vivo. On the contrary, direct inhibition of BCAT2 by RNA interference, or indirect inhibition by blocking system Xc– activity, triggers ferroptosis. Finally, our results demonstrate the synergistic effect of sorafenib and sulfasalazine in downregulating BCAT2 expression and dictating ferroptotic death, where BCAT2 can also be used to predict the responsiveness of cancer cells to ferroptosis-inducing therapies. Collectively, these findings identify a novel role of BCAT2 in ferroptosis, suggesting a potential therapeutic strategy for overcoming sorafenib resistance.

scholarly journals Branched-chain amino acid metabolism and alanine formation in rat diaphragm muscle in vitro. Effects of dichloroacetate

1984 ◽  
Vol 223 (3) ◽  
pp. 831-835 ◽  
Author(s):  
K Snell ◽  
D A Duff
Keyword(s):  
Amino Acid ◽  
Pyruvate Dehydrogenase ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Branched Chain Amino Acid ◽  
In Vitro Effects ◽  
Branched Chain

Dichloroacetate (which activates pyruvate dehydrogenase) decreases the release of alanine, pyruvate and lactate in hemidiaphragm incubations with valine. Dichloroacetate interferes with alanine formation by diverting pyruvate into oxidative pathways, which not only limits pyruvate availability for direct transamination to form alanine but also indirectly affects branched-chain amino acid transamination by limiting 2-oxoglutarate regeneration from glutamate.

scholarly journals Branched chain amino acid aminotransferase 2 Regulates Ferroptotic Cell Death in Cancer Cells

2020 ◽  
Author(s):  
Kang Wang ◽  
Zhengyang Zhang ◽  
Tsai Hsiang-i ◽  
Yanfang Liu ◽  
Ming Wang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cancer Cells ◽  
Therapeutic Strategy ◽  
Ectopic Expression ◽  
Branched Chain Amino Acid ◽  
Pancreatic Cancer Cells ◽  
Branched Chain

AbstractFerroptosis has been implicated as a tumor-suppressor function for cancer therapy. Recently the sensitivity to ferroptosis was tightly linked to numerous biological processes, including metabolism of amino acid. Here, using a high-throughput CRISPR/Cas9 based genetic screen in HepG2 cells to search for metabolic proteins inhibiting ferroptosis, we identified branched chain amino acid aminotransferase 2 (BCAT2) as a novel suppressor of ferroptosis. Mechanistically, ferroptosis inducers (erastin, sorafenib and sulfasalazine) activated AMPK/SREBP1 signaling pathway through ferritinophagy, which in turn inhibited BCAT2 transcription. We further confirmed that BCAT2 mediating the metabolism of sulfur amino acid, regulated intracellular glutamate level, whose activation by ectopic expression specifically antagonize system Xc– inhibition and protected liver and pancreatic cancer cells from ferroptosis in vitro and in vivo. Finally, our results demonstrate the synergistic effect of sorafenib and sulfasalazine in downregulating BCAT2 expression and dictating ferroptotic death, where BCAT2 can also be used to predict the responsiveness of cancer cells to ferroptosis-inducing therapies. Collectively, these findings identify a novel role of BCAT2 in ferroptosis, suggesting a potential therapeutic strategy for overcoming sorafenib resistance.

scholarly journals Supplementation of molasses and branched-chain amino acid to increase in vitro digestibility of ammoniated corn cob in ruminants feed

2018 ◽  
Vol 22 (4) ◽  
pp. 179
Author(s):  
Wisri Puastuti ◽  
Dwi Yulistiani ◽  
Eko Handiwirawan
Keyword(s):  
Amino Acid ◽  
Nutritive Value ◽  
Neutral Detergent Fiber ◽  
In Vitro Digestibility ◽  
In Vitro Test ◽  
Corn Cob ◽  
Branched Chain Amino Acid ◽  
Randomized Design ◽  
Branched Chain

<p>Corn cob contains high fiber and lignin which causes low nutritive value. The objective of the study was to improve the digestibility of ammoniated corn cob (CC) by supplementation of molasses and branched-chain amino acid (BCAA: valine, leucine and isoleucine). CC was processed by addition 3% urea. The first stage of in vitro test was done with 4 levels of molases 0, 5, 10 and 15% of dry matter (DM) of CC. The experiment was carried out using complete randomized design with 4 treatments and 4 replications. The second stage was also in vitro study of supplementation of two levels each for valine = V, leucine = L and isoleucine = I namely 0.1 and 0.2% of DM of ammoniated CC. There were 8 treatments combination of the BCAA as follow: A = V0.1 L0.1 I0.1; E = V0.2 L0.1 I0.1; B = V0.1 L0.1 I0.2; F = V0.2 L0.1 I0.2; C = V0.1 L0.2 I0.1; G = V0.2 L0.2 I0.1; D = V0.1 L0.2 I0.2; H = V0.2 L0.2 I0.2 and 1 control (V0.0 L0.0 I0.0). The experiments were done using completely randomized design with 9 treatments and 3 replications. The results showed that treated CC with urea was able to increase protein content by 78% (increased from 3.34% to 5.95%) while neutral detergent fiber (NDF) decreased by 15.4%, acid detergent fiber (ADF) by 7.9% and lignin 16.7%. Addition of molasses in ammoniated CC increased DM digestibility (P &lt;0.05) by 7.5% (41.9 vs 43.51-46.26%) and NDF by 17.7% (38.41 vs 43.76 – 46.31%). Supplementation of BCAA resulted in the highest DM, OM and NDF digestibility (P &lt;0.05) in the treatment of A, C, D and G. Compare to treament I, the digestibility of DM, OM and NDF in G treatment increased by 31.4%, 27.5% and 36.5%, respectively and produced the highest total population of rumen bacterial of 12.4 x 109 colonies /ml. It can be concluded that the digestibility of ammoniated CC increased by the supplementation of 5% molases and BCAA combination consisted of 0.2% valine, 0.2% leucine and 0.1% isoleucine.</p><p> </p><p>Kata kunci: Tongkol jagung, amoniasi, molases, asam amino bercabang.</p>

scholarly journals The effect of starvation on branched-chain 2-oxo acid oxidation in rat muscle

1984 ◽  
Vol 219 (1) ◽  
pp. 253-260 ◽  
Author(s):  
A J M Wagenmakers ◽  
J H Veerkamp
Keyword(s):  
Amino Acid ◽  
Protein Degradation ◽  
Specific Radioactivity ◽  
Acid Oxidation ◽  
Oxidative Decarboxylation ◽  
Precursor Pool ◽  
Oxidation Rates ◽  
Branched Chain Amino Acid ◽  
Endogenous Protein ◽  
Branched Chain

Oxidative-decarboxylation rates of branched-chain amino acids in rat hemidiaphragm and of branched-chain 2-oxo acids in hemidiaphragm, soleus muscle and heart slices of 110-120 g rats were increased considerably by 3-4 days of starvation, when they were calculated from the specific radioactivity in the medium. When the supply from endogenous protein degradation to the oxidation-precursor pool was severely limited by transaminase inhibitors, oxidative-decarboxylation rates of branched-chain 2-oxo acids rose significantly. Since this apparent increase was relatively larger in preparations from fed rats than from 3-days-starved rats, the differences in oxidation rates with nutritional state became less or even not significant. With rat heart the smaller dilution of the oxidation precursor pool after starvation is in accordance with the reported decrease in protein breakdown. Since protein degradation increases with starvation in skeletal muscles, we suggest that the amino acid pool arising from protein degradation is more segregated from the oxidation precursor pool in muscles from starved than from fed rats. We conclude that starvation increases branched-chain amino acid and 2-oxo acid oxidation in skeletal and cardiac muscle considerably less than has been suggested by previous studies.

Branched chain amino acid imbalance selectively inhibits the growth of gastric carcinoma cells in vitro

2003 ◽  
Vol 23 (9) ◽  
pp. 1279-1290 ◽  
Author(s):  
Xueying Sun ◽  
Nan Zhang ◽  
Ke Li ◽  
Meng Liu ◽  
Xuting Zhi ◽  
...  
Keyword(s):  
Amino Acid ◽  
Gastric Carcinoma ◽  
Carcinoma Cells ◽  
Branched Chain Amino Acid ◽  
Amino Acid Imbalance ◽  
Branched Chain
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