Thermostable S-alkylcysteine alpha, beta-lyase from a thermophile: purification and properties.
S-Alkylcysteine alpha, beta-lyase was found in a thermophile, Bacillus sp. 41A, which was newly isolated from soil, and purified to homogeneity from the cell extract. The enzyme has a molecular weight of about 76,000, and is composed of two subunits identical in molecular weight (39,000). The enzyme requires pyridoxal 5'-phosphate as a coenzyme, and catalyzes alpha, beta-elimination of S-methyl-L-cysteine and its analogs such as S-ethyl-L-cysteine, L-djenkolate, L-cystine, Se-methyl-L-selenocysteine, and O-methyl-DL-serine. However, S-methyl-D-cysteine, D-cystine, L-methionine, and L-norleucine were inert. The enzyme also catalyzes the beta-replacement reaction of S-methyl-L-cysteine with various thiols to yield the corresponding S-substituted cysteines. In addition to S-methyl-L-cysteine, Se-methyl-L-selenocysteine and O-methyl-DL-serine also serve as beta-substituent acceptors in the beta-replacement reaction. The enzyme is most active at 70 degrees C and stable at high temperatures. Automated Edman degradation provided the N-terminal sequence of the first 44 amino acids. The amino acid sequence in the vicinity of the lysyl residue to which pyridoxal 5'-phosphate is bound, was -Lys-His-Gln-Arg- by Edman degradation of the pyridoxyl peptide obtained by digestion with trypsin after reduction with sodium borohydride.
Institute for Chemical Research, Kyoto University, Japan.
H
H
Kamitani
N
N
Esaki
H
H
Tanaka
K
K
Soda
D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology*; D001665:Binding Sites; D013437:Carbon-Sulfur Lyases; D003470:Culture Media; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D004795:Enzyme Stability; D006358:Hot Temperature; D008190:Lyases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013379:Substrate Specificity
D003470:Culture Media; C008425:S-methylcysteine; D008190:Lyases; D013437:Carbon-Sulfur Lyases; C019969:S-alkylcysteine lyase; D003545:Cysteine