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Lactobacillus reuteri DSM 20016: purification and characterization of a cystathionine γ-lyase and use as adjunct starter in cheesemaking

Published online by Cambridge University Press:  06 September 2002

MARIA DE ANGELIS
Affiliation:
Dipartimento di Scienze degli Alimenti (Sezione di Microbiologia Agro-Alimentare), Università degli Studi di Perugia, Italy
ÁINE C. CURTIN
Affiliation:
Department of Food Science, Food Technology and Nutrition (Food Chemistry Section), University College, Cork, Ireland
PAUL L. H. McSWEENEY
Affiliation:
Department of Food Science, Food Technology and Nutrition (Food Chemistry Section), University College, Cork, Ireland
MICHELE FACCIA
Affiliation:
Dipartimento di Produzioni Animali, Università degli Studi di Bari, Italy
MARCO GOBBETTI
Affiliation:
Dipartimento di Protezione delle Piante e Microbiologia Applicata, Università degli Studi di Bari, Italy

Abstract

A homo-tetrameric ∼160-kDa cystathionine γ-lyase was purified to homogeneity from Lactobacillus reuteri DSM 20016 by four chromatographic steps. The activity was pyridoxal-5′-phosphate dependent and the enzyme catalyzed the α,γ-elimination reaction of L-cystathionine, producing L-cysteine, ammonia and α-ketobutyrate. The enzyme was active towards a range of amino acids and amino acid derivatives, including methionine. The pH and temperature optima were found to be 8.0 and 35 °C, respectively. Isoelectric pH (pI) was ∼5.0 as determined by two-dimensional electrophoresis. Sensitivity to chemical inhibitors was typical of lactococcal cystathionine γ- and β-lyases, except it was inhibited by sulphydryl reagents. The N-terminal sequence was MKFNTQLIHGGNSED, which had 100% homology with cystathionine β-lyase of Lb. reuteri 104R (Accession Number CAC05298). Lb. reuteri DSM 20016, together with 10 other strains of non-starter lactic acid bacteria, was used as adjunct starter in the production of miniature Canestrato Pugliese-like cheeses. After 40 d ripening, the water-soluble extract of the cheeses with added Lactobacillus fermentum DT41 and Lb. reuteri DSM 20016 contained the highest enzyme activities on cystathionine and methionine substrates. Determinations of methanethiol, dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide in the miniature cheeses confirmed the findings of enzyme activities.

Type
Research Article
Copyright
© Proprietors of Journal of Dairy Research 2002

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