title: Cloning and characterization of two Lactobacillus casei genes encoding a cystathionine lyase.
abstract: Volatile sulfur compounds are key flavor compounds in several cheese types. To better understand the metabolism of sulfur-containing amino acids, which certainly plays a key role in the release of volatile sulfur compounds, we searched the genome database of Lactobacillus casei ATCC 334 for genes encoding putative homologs of enzymes known to degrade cysteine, cystathionine, and methionine. The search revealed that L. casei possesses two genes that putatively encode a cystathionine beta-lyase (CBL; EC 4.4.1.8). The enzyme has been implicated in the degradation of not only cystathionine but also cysteine and methionine. Recombinant CBL proteins catalyzed the degradation of L-cystathionine, O-succinyl-L-homoserine, L-cysteine, L-serine, and L-methionine to form alpha-keto acid, hydrogen sulfide, or methanethiol. The two enzymes showed notable differences in substrate specificity and pH optimum.
authors.affiliation: Agroscope Liebefeld-Posieux Research Station ALP, Schwarzenburgstrasse 161, Bern, Switzerland. stefan.irmler@alp.admin.ch
authors.forename: Stefan
authors.initials: S
authors.lastname: Irmler
authors.forename: Sylvie
authors.initials: S
authors.lastname: Raboud
authors.forename: Beata
authors.initials: B
authors.lastname: Beisert
authors.forename: Doris
authors.initials: D
authors.lastname: Rauhut
authors.forename: Hélène
authors.initials: H
authors.lastname: Berthoud
mesh_terms: D003001:Cloning, Molecular; D003540:Cystathionine / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004795:Enzyme Stability; D006714:Homoserine / Q000031:analogs & derivatives / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007651:Keto Acids / Q000378:metabolism; D007780:Lacticaseibacillus casei / Q000201:enzymology* / Q000235:genetics*; D008190:Lyases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D007651:Keto Acids; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; C014196:O-succinylhomoserine; C005231:methylmercaptan; D003540:Cystathionine; D012694:Serine; D006714:Homoserine; D008715:Methionine; D008190:Lyases; C019965:cystathionine beta-lyase; D003545:Cysteine; D006862:Hydrogen Sulfide