• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.794-798
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• 1995

Deamidation by neutrase on glutaminyl and asparaginyl residues of protein was examined. The optimum pH and temperature for BSA(bovine serum albumin) deamidation by neutrase were 10 and $20^{\circ}C$, respectively. The incubation for 3 hrs under the optimum condition removed 24% of amide groups and hydrolyzed 2.9% of peptide bonds. Deamidation by neutrase was superior to that by pronase, bromelain, or ficin. Deamidation degrees of egg albumin, soy protein isolate and casein by neutrase under the optimum condition were about 20%, 14% and 14%, respectively. However, relatively high degree of peptide hydrolysis was accompanied with casein deamidation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.5
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• pp.811-815
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• 1995

Effect of deamidation with Neutrase on the solubility of bovin serum albumin(BSA), egg albumin(EA), soy protein isolate(SPI) was investigated. Solubility of deamidated BSA in distilled water was decreased from 98% to 83% against native BSA at pH 4~8, minimum solubility of deamidated BSA was pH 6. Solubilities of native BSA and deamidated BSA in 0.2M NaCl solution were shown 100% as compared greately decreasing both solubilities in 1.0M NaCl at acidic pH. According to deamidation, solubility of EA in distilled water was increased below pH 4 and above pH 6, while solubility of EA in NaCl solution was decreased by deamidation at acidic pH. Solubility of SPI in distilled water was greately increased by deamidation at overall pH, deamidation was increased solubility in NaCl solution above pH 5. There was, however, no difference on solubility by deamidation below pH 5.

• Mass Spectrometry Letters
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• v.14 no.2
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• pp.48-55
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• 2023

This study compares the efficiency of weak acid hydrolysis (WAH) using formic acid (FA) and hydrochloric acid (HCl) in the analysis of myoglobin peptides. WAH using 2% and 5% formic acid resulted in the identification of 32 peptides, with varying degrees of cleavage at the C-terminus of aspartic acid residues. HCl WAH with different concentrations demonstrated an increase in the total number of identified peptides but a decrease in fully cleaved peptides as the HCl concentration increased. Notably, deamidation was observed during HCl WAH but not in FA WAH. The addition of HCl WAH after FA WAH provided a similar pattern to HCl WAH, with slightly higher levels of hydrolysis. These findings highlight distinct cleavage patterns and deamidation effects between FA and HCl in the context of WAH.

• Molecules and Cells
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• v.37 no.11
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• pp.819-826
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• 2014

Protein modifications of recombinant pharmaceuticals have been observed both in vitro and in vivo. These modifications may result in lower efficacy, as well as bioavailability changes and antigenicity among the protein pharmaceuticals. Therefore, the contents of modification should be monitored for the quality and efficacy of protein pharmaceuticals. The interface of EPO and its receptor was visualized, and potential amino acids interacting on the interface were also listed. Two different types of modifications on the interface were identified in the preparation of rHu-EPO BRP. A UPLC/Q-TOF MS method was used to evaluate the modification at those variants. The modification of the oxidized variant was localized on the Met54 and the deamidated variants were localized on the Asn47 and Asn147. The extent of oxidation at Met54 was 3.0% and those of deamidation at Asn47 and Asn147 were 2.9% and 4.8%, respectively.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.600-604
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• 1989

In order to find the rational methods for improving the thermal stability of subtilisin Carlsberg, the mechanisms of irreversible thermoinactivation of the enzyme were studied at $90^{\circ}C.$ At pH 4, the main process was hydrolysis of peptide bond. This process followed first order kinetics, yielding a rate constant of $1.26\;{\times}\;10^{-1}h^{-1}$. Hydrolysis of peptide bond of PMS-subtilisin occurred at various sites, which produced new distinct fragments of molecular weights of 27.2 KD, 25.9 KD, 25.0 KD, 22.3 KD, 19.0 KD, 17.6 KD, 16.5 KD, 15.7 KD, 15.0 KD, 13.7 KD, and 12.7 KD. Most of the new fragments originated from the acidic hydrolysis at the C-side of aspartic acid residues. However 25.0 KD, 15.7 KD, and 13.7 KD which could not be removed in purification steps stemmed from the autolytic cleavage of subtilisin. The minor process at pH 4 was deamidation at asparagine and/or glutamine residues and some extend of aggregation was also observed. However, the aggregation was main process at pH 7 with a first order kinetic constant of $16 h^{-1}.$ At pH 9, the main process seemed to be combination of deamidation and cleavage of peptide bond.

• Food Science of Animal Resources
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• v.34 no.2
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• pp.207-213
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• 2014

This study investigated the effects of microbial transglutaminase (MTGase) and pH-shift processing on the functional properties of porcine myofibrillar proteins (MP). The pH-shift processing was carried out by decreasing the pH of MP suspension to 3.0, followed by re-adjustment to pH 6.2. The native (CM) and pH-shifted MP (PM) was reacted with and without MTGase, and the gelling and emulsion characteristics were compared. To compare the pH-shifted MTGase-treated MP (PT), deamidation (DM) was conducted by reacting MTGase with MP at pH 3.0. Rigid thermal gel was produced by MTGase-treated native MP (CT) and PT. PM and DM showed the lowest storage modulus (G') at the end of thermal scanning. Both MTGase and pH-shifting produced harder MP gel, and the highest gel strength was obtained in PT. All treatments yielded lower than CM, and CT showed significantly higher yield than PM and DM treatments. For emulsion characteristics, pH-shifting improved the emulsifying ability of MP-stabilized emulsion, while the treatments had lower emulsion stability. PM-stabilized emulsion exhibited the lowest creaming stability among all treatments. The emulsion stability could be improved by the usage of MTGase. The results indicated that pH-shifting combined with MTGase had a potential application to modify or improve functional properties of MP in manufacturing of meat products.

• Mass Spectrometry Letters
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• v.5 no.4
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• pp.95-103
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• 2014

Characterization and studies of proteome are challenging because biological samples are complex, with a wide dynamic range of abundance. At present the proteins are identified by digestion into peptides, with subsequent identification of the peptides by mass spectrometry (MS). MS is a powerful technique for the purpose, but it cannot identify every peptide in such complex mixtures simultaneously. For accurate analysis and quantification it is important to separate the peptides first by chromatography into fractions of a size that MS can handle. With these less complex fractions, the probability is increased of identifying peptides of low abundance that would otherwise experience ion suppression effects due to the presence of peptides of high abundance. Enrichment for peptides with certain post-translational modifications helps to increase their detection rates as well. Electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) is a mixed-mode chromatographic technique which combines the use of electrostatic repulsion and hydrophilic interaction. This review provides an overview of ERLIC and its various proteomics applications. ERLIC has been demonstrated to have good orthogonality to reverse phase liquid chromatography (RPLC), making it useful as a first dimension in multidimensional liquid chromatography (MDLC) and fractionation of digests in general. Peptides elute in order of their isoelectric points and polarity. ERLIC has also been successfully utilized for the enrichment for phosphopeptides and glycopeptides, facilitating their identification. In addition, it is promising for the study of peptide deamidation. ERLIC performs comparably well or better than established methods for these various applications, and serves as a viable and efficient workflow alternative.

• KSBB Journal
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• v.8 no.4
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• pp.405-408
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• 1993

Absidia zychae NRIC 1199 produced two forms of carboxypeptidase(CPZ-1 and CPZ-2) which were distinguished in their isoelectric points but had almost identical properties(1). The amino acid sequences for the N-terminal of both enzymes were the same (Tyr-Thr-Ser-Pro-Lys-Leu-Xaa-Asp-Pro-Asp-Val) and any significant difference was not observed between amino acid compositions of the two enzymes. The ouchterlony double diffusion technique using antibody raised against the CPZ-2 protein demonstrated a good cross-reaction between CPZ-1 and CPZ-2 Genomic Southern analysis showed only one gene encoding CPZ in the genome of Absidia zychae. However, a significant difference between two enzymes was observed on peptide map using Staphylococcus aureus V8 protease, distinguishable only one band, indicating that multiple forms of CPZ are caused by post-translational modification, such as deamidation.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.617-626
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• 2011

Transglutaminase from Streptomyces mobaraensis is an enzyme of unknown function that cross-links proteins to high molecular weight aggregates. Previously, we characterized two intrinsic transglutaminase substrates with inactivating activities against subtilisin and dispase. This report now describes a novel substrate that inhibits papain, bromelain, and trypsin. Papain was the most sensitive protease; thus, the protein was designated Streptomyces papain inhibitor (SPI). To avoid transglutaminase-mediated glutamine deamidation during culture, SPI was produced by Streptomyces mobaraensis at various growth temperatures. The best results were achieved by culturing for 30-50 h at $42^{\circ}C$, which yielded high SPI concentrations and negligibly small amounts of mature transglutaminase. Transglutaminasespecific biotinylation displayed largely unmodified glutamine and lysine residues. In contrast, purified SPI from the $28^{\circ}C$ culture lost the potential to be cross-linked, but exhibited higher inhibitory activity as indicated by a significantly lower $K_i$ (60 nM vs. 140 nM). Despite similarities in molecular mass (12 kDa) and high thermostability, SPI exhibits clear differences in comparison with all members of the wellknown family of Streptomyces subtilisin inhibitors. The neutral protein (pI of 7.3) shares sequence homology with a putative protein from Streptomyces lavendulae, whose conformation is most likely stabilized by two disulfide bridges. However, cysteine residues are not localized in the typical regions of subtilisin inhibitors. SPI and the formerly characterized dispase-inactivating substrate are unique proteins of distinct Streptomycetes such as Streptomyces mobaraensis. Along with the subtilisin inhibitory protein, they could play a crucial role in the defense of vulnerable protein layers that are solidified by transglutaminase.