Oxidative modification of amino acids in porcine myofibrillar protein isolates exposed to three oxidizing systems

2007 ◽  
Vol 103 (2) ◽  
pp. 607-616 ◽  
Author(s):  
Donkeun Park ◽  
Youling L. Xiong
2021 ◽  
Vol 86 (3) ◽  
pp. 824-833
Author(s):  
Zengfang Zhu ◽  
Xiaoying Mao ◽  
Qingzhi Wu ◽  
Jian Zhang ◽  
Xiaorong Deng

2018 ◽  
Vol 314 (5) ◽  
pp. E457-E467 ◽  
Author(s):  
Jorn Trommelen ◽  
Imre W. K. Kouw ◽  
Andrew M. Holwerda ◽  
Tim Snijders ◽  
Shona L. Halson ◽  
...  

The purpose of this study was to determine the impact of ingesting 30 g casein protein with and without 2 g free leucine before sleep on myofibrillar protein synthesis rates during postexercise overnight recovery. Thirty-six healthy young men performed a single bout of resistance-type exercise in the evening (1945) after a full day of dietary standardization. Thirty minutes before sleep (2330), subjects ingested 30 g intrinsically l-[1-13C]phenylalanine-labeled protein with (PRO+leu, n = 12) or without (PRO, n = 12) 2 g free leucine, or a noncaloric placebo (PLA, n = 12). Continuous intravenous l-[ ring-2H5]phenylalanine, l-[1-13C]leucine, and l-[ ring-2H2]tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole body protein net balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into myofibrillar protein. Protein ingestion before sleep improved overnight whole body protein net balance ( P < 0.001). Myofibrillar protein synthesis rates did not differ significantly between treatments as assessed by l-[ ring-2H5]phenylalanine (0.057 ± 0.002, 0.055 ± 0.002, and 0.055 ± 0.004%/h for PLA, PRO, and PRO+leu, respectively; means ± SE; P = 0.850) or l-[1-13C]leucine (0.080 ± 0.004, 0.073 ± 0.004, and 0.083 ± 0.006%/h, respectively; P = 0.328). Myofibrillar l-[1-13C]phenylalanine enrichments increased following protein ingestion but did not differ between the PRO and PRO+leu treatments. In conclusion, protein ingestion before sleep improves whole body protein net balance and provides amino acids that are incorporated into myofibrillar protein during sleep. However, the ingestion of 30 g casein protein with or without additional free leucine before sleep does not increase muscle protein synthesis rates during postexercise overnight recovery.


2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 642-642
Author(s):  
Glory Madu ◽  
Olasunkanmi Adegoke

Abstract Objectives Branched-chain amino acids (BCAAs) are essential amino acids that are crucial for skeletal muscle anabolism. Thus, alterations in their levels are associated with muscle atrophic diseases such as cancer, chronic inflammatory and neurological disorders. Others have linked impairments in BCAA metabolism to the development of insulin resistance and its sequelae. Compared to the effects of theses amino acids, much less is known on how impairment in BCAA catabolism affects skeletal muscle. BCAA catabolism starts with the reversible transamination by the mitochondrial enzyme branched-chain aminotransferase 2 (BCAT2). This is followed by the irreversible carboxylation, catalyzed by branched-chain ketoacid dehydrogenase (BCKD) complex. We have shown that BCAT2 and BCKD are essential for the differentiation of skeletal myoblasts into myotubes. Here, we investigated the effect of depletion of BCAT2 or of E1a subunit of BCKD in differentiated myotubes. Methods On day 4 of differentiation, L6 myotubes were transfected with the following siRNA oligonucleotides: scrambled (control), BCAT2, or E1a subunit of BCKD. Results Forty-eight hours after transfection, compared to control or BCAT2 siRNA group, we observed improved myotube structure in BCKD-depleted cells. BCKD depletion augmented myofibrillar protein levels: myosin heavy chain (MHC, 2-fold) and tropomyosin (4-fold), P &lt; 0.05, n = 3. To further analyze the increase in myofibrillar protein content, we examined signaling through mTORC1 (mechanistic target of rapamycin complex 1), a vital complex necessary for skeletal muscle anabolism. BCKD depletion increased the phosphorylation of mTORC1 upstream activator AKT (52%, P &lt; 0.05, n = 3), and of mTORC1 downstream substrates by 25%-86%, consistent with the increase in myofibrillar proteins. Finally, in myotubes treated with the catabolic cytokine (tumor necrosis factor-a), BCKD depletion tended to increase the abundance of tropomyosin (a myofibrillar protein). Conclusions We showed that depletion of BCKD enhanced myofibrillar protein content and anabolic signaling.  If these data are confirmed in vivo, development of dietary and other interventions that target BCKD abundance or functions may promote muscle protein anabolism in individuals with muscle wasting conditions. Funding Sources MHRC, NSERC York U.


1993 ◽  
Vol 58 (2) ◽  
pp. 274-277 ◽  
Author(s):  
T.G. UIJTTENBOOGAART ◽  
T.L. TRZISZKA ◽  
F.J.G. SCHREURS

1972 ◽  
Vol 126 (1) ◽  
pp. 237-249 ◽  
Author(s):  
M. C. Schaub ◽  
S. V. Perry ◽  
W. Häcker

1. Electrophoretically homogeneous calcium-sensitizing factor was prepared from the troponin complex by chromatography successively on sulphoethyl-Sephadex and on diethyl-(2-hydroxypropyl)aminoethyl-Sephadex in 6m-urea. It is a protein containing 53% of polar amino acids, of which a net excess consists of acidic residues. 2. On gel filtration the calcium-sensitizing factor was shown to be the only myofibrillar protein that bound 45Ca2+ tightly in the presence of 2–6m-urea. 3. Calcium-sensitizing factor effectively neutralized the effect of the inhibitory factor on the ATPase activities of actomyosin systems. Tropomyosin was essential for the regulation, by changes in the Ca2+ concentration, of the neutralizing effect of calcium-sensitizing factor on the inhibitory factor. 4. Prolonged exposure to chelators of Ca2+ produced an irreversibly modified form of calcium-sensitizing factor of higher electrophoretic mobility at pH8.6. The modified form neutralized the inhibitory factor action but this property could no longer be controlled by the Ca2+ concentration in the presence of tropomysin. 5. The calcium-sensitizing factor and tropomyosin could be replaced by their carboxymethylated derivatives in the relaxing-protein system.


2006 ◽  
Vol 54 (12) ◽  
pp. 4445-4451 ◽  
Author(s):  
Donkeun Park ◽  
Youling L. Xiong ◽  
Amy L. Alderton ◽  
Tooru Ooizumi

Meat Science ◽  
2014 ◽  
Vol 96 (4) ◽  
pp. 1432-1439 ◽  
Author(s):  
Feibai Zhou ◽  
Mouming Zhao ◽  
Haifeng Zhao ◽  
Weizheng Sun ◽  
Chun Cui

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