L-methionine-y-lyase

L-homo serine L-methionine-y-lyase Clostridium, Pseudomonas 133... 

Tanaka, H., Esaki, N., and Soda, K. (1985). A versatile bacterial enzyme L-methionine y-lyase. Enzyme Microbiol. Technol. 7,530-537. 

Sulfur-containing amino acids, especially L-methionine, serve as precursors for MT and the many materials derived from this compound, such as DMS, DMDS, DMTS, methyl thioacetate, etc. The most direct route for the L-methionine MT conversion is by demethiolation (Equation 4) catalyzed by methionine y-lyase, EC 4.4.1.11 ... 

Reliable enzymatic assays for SeMet are not available as specific SeMet metabolizing enzymes have not been identified and enzymes such as glutamine transaminase react with Met equally as well as with SeMet (Blazon et al., 1994). However, with some enzymes reaction rates for SeMet and Met differ sufficiently to be of some use in SeMet analysis. For example, SeMet is a better substrate than Met for the a,y-elimination by i.-methionine y-lyase of Pseudomonas putida (Esaki et al., 1979). The adenosyl methionine transferase from rat liver reacts with L-SeMet at 51% of the rate with L-Met, and with the corresponding D-isomers at only 13 and 10% of the rate of L-Met (Pan and Tarver, 1967). Other adenosyl methionine transferases, such as that from yeast, react with SeMet more rapidly and with higher stereoselectivity than with Met, providing an indirect means for SeMet determination (Mudd and Cantoni, 1957 Sliwkowski, 1984 Uzar and Michaelis, 1994). 

Methionine 7-lyase, in contrast, has been purified from Aeromonas sp., Pseudomonas putida and Clostridium sporogenes (361. This enzyme effects a a,y-elimination of methanethiol and ammonia from L-methionine with the direct formation of 2-ketobutyrate ... 

Elevated minimum methionine dependence of most and possibly all types of tumor cells relative to normal cells has been demonstrated. The L-methionine a-deamino-y-mercaptomethane lyase (methioninase, METase) gene from Pseudomonas putida has been previously cloned in Escherichia... 

Hori, H., Takabayashi, K., Orvis, L., Carson, D.A., and Nobori, T., 1996, Gene cloning and characterization of Pseudomonas putida L-methionine-a-deamino-y-mercaptomethane lyase. Cancer Res. 56 2116-2122. 

The major developmental change which takes place In both brain and liver is the postnatal activation of the transsulfuration pathway of methionine metabolism. The net result of this pathway is the transfer of the sulfur atom from homocysteine to the carbon skeleton of serine to form cysteine. This conversion is mediated by two enzymes cystathionine synthase (L-serine hydro-lyase adding homocysteine, EC 4.2.1.22) which catalyzes the 3-activation of serine and the addition of homocysteine to form the thio-ether, cystathionine cystathionase (EC 4.4.1.1) which catalyzes the y-cleavage of cystathionine to form cysteine (Fig. 1). Both of these enzymes catalyze reactions other than those described above although their importance vivo is uncertain (Tallan et al., 1974). In mature mammals, activities both of cystathionine synthase and of cystathionase are present in brain and liver, although cystathionase activity in... 

LeuDH L-Leucine, L-valine, L-branched chain amino acids, 2-oxoisovalerate, 2-oxo branched chain acids, 2-oxoisocaproate, L-methionine (methioine y-lyase), aminopeputidase, o-amino acid aminotransferase, tripeptide aminopeptidase, stereospecificity of hydrogen transfer of NADH (low substrate amino acid racemase), maple syrup urine disease, hyperinsulinemic euglycemic clamps... 

Several PLP-dependent enzymes catalyze elimination and replacement reactions at the y-carbon of substrates, an unusual process which provides novel routes for mechanism-based inactivation. An example of this class of enzymes is cystathionine y-synthase [0-succinylhomoserine (thiol)-lyase], which converts (7-succinyl-L-homoserine and L-cysteine to cystathionine and succinate as part of the bacterial methionine biosynthetic pathway (Walsh, 1979, p. 823). Formation of a PLP-stabilized o-carbanion intermediate activates the )8-hydrogen for abstraction, yielding j8-carbanion equivalents and allowing elimination of the y-substituent. The resulting j8,y-unsaturated intermediate serves as an electrophilic acceptor for the replacement nucleophile. Suitable manipulation of the j8-carbanion intermediate allows strategies for the design of inactivators which do not affect enzymes which abstract only the a-hydrogen. 

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