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Titolo:
Partial purification and characterization of two aminotransferases from Lactococcus lactis subsp cremoris B78 involved in the catabolism of methionine and branched-chain amino acids
Autore:
Engels, WJM; Alting, AC; Arntz, MMTG; Gruppen, H; Voragen, AGJ; Smit, G; Visser, S;
Indirizzi:
NIZO Food Res, Dept Flavour & Nat Ingredients, NL-6710 BA Ede, NetherlandsNIZO Food Res Ede Netherlands NL-6710 BA ts, NL-6710 BA Ede, Netherlands NIZO Food Res, Dept Prod Technol, NL-6710 BA Ede, Netherlands NIZO Food Res Ede Netherlands NL-6710 BA ol, NL-6710 BA Ede, Netherlands Univ Wageningen & Res Ctr, Dept Food Sci, Wageningen, Netherlands Univ Wageningen & Res Ctr Wageningen Netherlands ageningen, Netherlands
Titolo Testata:
INTERNATIONAL DAIRY JOURNAL
fascicolo: 7, volume: 10, anno: 2000,
pagine: 443 - 452
SICI:
0958-6946(2000)10:7<443:PPACOT>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
WATER-SOLUBLE FRACTION; CELL-FREE-EXTRACTS; ESCHERICHIA-COLI; CHEESE FLAVOR; GAMMA-LYASE; BREVIBACTERIUM-LINENS; STARTER PEPTIDASES; VOLATILE COMPOUNDS; CHEDDAR CHEESE; BACTERIA;
Keywords:
aminotransferases; Lactococcus lactis; methionine; cheese flavour;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
51
Recensione:
Indirizzi per estratti:
Indirizzo: Engels, WJM NIZO Food Res, Dept Flavour & Nat Ingredients, POB 20, NL-6710BA Ede, Netherlands NIZO Food Res POB 20 Ede Netherlands NL-6710 BA , Netherlands
Citazione:
W.J.M. Engels et al., "Partial purification and characterization of two aminotransferases from Lactococcus lactis subsp cremoris B78 involved in the catabolism of methionine and branched-chain amino acids", INT DAIRY J, 10(7), 2000, pp. 443-452

Abstract

Transamination of methionine and other amino acids followed by conversion of the resulting alpha -keto acids by enzymes from the mesophilic starter organism Lactococcus lactis subsp. cremoris B78 was studied. Two aminotransferases, displaying activity towards methionine, were partially purified andcharacterized. The enzymes most likely were branched-chain aminotransferases, since their activity towards valine, leucine and isoleucine was even higher than towards methionine. The enzymes, AT-A and AT-B, both showed a molecular mass of approximately 75 kDa and consisted of two identical subunits, each with a molecular mass of approximately 40 kDa. AT-A and AT-B also had a broad substrate specificity for the amino-group acceptor, alpha -ketoglutaric acid being the preferred cosubstrate. The enzymes catalyzed the conversion of methionine to 4-methylthio-2-ketobutyric acid, which was subsequently converted to methanethiol and dimethyldisulphide. The formation of these and other volatile sulfur compounds is considered to play an important role in the development of cheese flavour. Both AT-A and AT-B had a rather high optimum temperature, 45-50 degreesC, and a pH optimum of 8. However, under simulated cheese-ripening conditions (10-15 degreesC and pH 5.2-5.4) sufficient activity remained for conversion of methionine. (C) 2000 Elsevier Science Ltd. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 11/07/20 alle ore 11:16:53