L-Methionine

The cells of A. oryzae are not a convenient source of the hydrolase enzyme, and their use is hardly an advance on the technology which Pasteur had introduced about a century earlier (see Chapter 1). It is not an active fermentation process like the steroid hydroxylations. The cells are grown and harvested before being added to the conversion mixture consequently, these cells will contain not only the enzyme which is catalysing the hydrolysis but also many others, some of which could oxidize the methionine once it is formed, or catalyse the release of soluble material from the cells. All of these impurities simply contaminate the reaction mixture. The cells recovered from the reaction mixture could be used again in a subsequent 

Systems similar to that described in Section 6.4.1 are used for the resolution of other racemic amino acid derivatives the preparation of D-amino acids 

The hydantoinases are particularly useful enzymes because the hydan-toins are intermediates in the synthesis of many amino acids. Enzymes with specificities for the D- or the L-enantiomers are available. The enzyme from Pseudomonas striata is most active against dihydrouracil, and it is possible that this is its natural substrate. The most active substrates amongst the hydantoins are those formed from the neutral aliphatic amino acids, but several phenylglydne analogues are also hydrolysed. 

300 )um and a wall thickness of some 50/xm. The aqueous phase passes through the internal lumina of the fibres, while the organic phase flows over their external surfaces. The hydrolysis occurs as the ester passes across the membrane. This process, which Sepracor Inc. developed, may not be a fully commercial process for the synthesis of 4-hydroxy-o-phenylglycine, but it certainly represents an innovative use of an enzyme in a reaction where its substrate is poorly soluble in water. On the other hand, the Kanegafuchi company does use the hydantoinase process to manufacture some of the 1,200 tonnes of amino acid side chain needed to manufacture the estimated 2,800 tonnes of amoxicillin produced each year. 

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Sulfur deficiency usually is not a problem for mminants because the mminal microflora can utilize sulfur-containing amino acids. A deficiency can occur, however, when an NPN source is fed. L-Methionine [63-68-3] is the most biologically available source of sulfur (21). Various sulfates are intermediate in sulfur avadabiHty, and elemental sulfur is the least available source of sulfur. 

The sulfur amino acid content of soy protein can be enhanced by preparing plasteins from soy protein hydrolysate and sources of methionine or cystine, such as ovalbumin hydrolysate (plastein AB), wool keratin hydrolysate (plastein AC), or L-methionine ethyl ester [3082-77-7] (alkaU saponified plastein) (153). Typical PER values for a 1 2 mixture of plastein AC and soybean, and a 1 3 mixture of alkah-saponified plastein and soybean protein, were 2.86 and 3.38, respectively, as compared with 1.28 for the soy protein hydrolysate and 2.40 for casein. 

In the case of hyperphenylalaninaemia, which occurs ia phenylketonuria because of a congenital absence of phenylalanine hydroxylase, the observed phenylalanine inhibition of proteia synthesis may result from competition between T.-phenylalanine and L-methionine for methionyl-/RNA. Patients sufferiag from maple symp urine disease, an inborn lack of branched chain oxo acid decarboxylase, are mentally retarded unless the condition is treated early enough. It is possible that the high level of branched-chain amino acids inhibits uptake of L-tryptophan and L-tyrosiae iato the brain. Brain iajury of mice within ten days after thek bkth was reported as a result of hypodermic kijections of monosodium glutamate (MSG) (0.5—4 g/kg). However, the FDA concluded that MSG is a safe kigredient, because mice are bom with underdeveloped brains regardless of MSG kijections (106). 

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

L-methionine DL-methionine + Asp D-amino acid oxidase + transaminase Trigonopsis variabilis ... 

Currently available proteins are all deficient to greater or lesser extent in one or more of the essential amino acids. The recently advanced plastein reaction (229) has made it possible to use protein itself as substrate and to attach amino acid esters to the protein with high efficiency. By this method, soy bean protein (which is deficient in methionine) has been improved to the extent of having covalently attached L-methionine at 11%. 

Methicillin — see Penicillin, 2,6-dimethoxyphenyl-Methidathion insecticidal activity, 6, 576 as insecticide, 1, 196 Methine, dipteridyl-synthesis, 3, 303 Methine dyes, 1, 323-325, 332 L-Methionine, S-adenosyl-in metabolic iV-methylation, 1, 236 Methionine, dehydro- C NMR, 6, 139 X-ray crystallography, 6, 136 Methiothepin... 

S-Methyl-L-methionine chloride (Vitamin U) [1115-84-0] M 199.5, [a]p +33 (0.2M pK[ 1.9, pKj 7.9. Likely impurities are methionine, methionine sulfoxide and methionine sulfone. from water by adding a large excess of EtOH. Stored in a cool, dry place, protected from light. 

Several years ago Makino et al. 86) studied the influence of anions on the conformation of poly-[L-methionine-S-methylsulfonium] salts in solution. They found that especially perchlorate will induce a-helix formation whereas Cl- and Br do not. Since then several authors 87 92) have found a similar a-helix inducing effect in the case of poly-L-lysine (Lys) and other BPAA at low pH-values where the polymer molecules usually attain an extended conformation due to the electrostatic repulsion of the ammonium groups. Therefore, the a-helix inducing effect is obviously an... 

Similarly, by adding analogs of L-methionine, the methylation of C6 is inhibited, resulting in the formation of 6-demethylchlortetracycline. The analogs that may be used include D-methionine and ethionine. 

The plant is mainly used for L-methionine, L-valine, L-phenylalanine. The German firm Degussa AG... 

Degussa AG uses immobilised acylase to produce a variety of L-amino adds, for example L-methionine (80,000 tonnes per annum). The prindples of the process are the same as those of the Tanabe-process, described above. Degussa uses a new type of reactor, an enzyme membrane reactor, on a pilot plant scale to produce L-methionine, L-phenylalanine and L-valine in an amount of 200 tonnes per annum. 

The body excretes platinum in various ways, mainly through urine the complex Pt(L-methionine-SN)2 is one of the few characterized products [206]. 

Thiourea and allylthiourea (20), D-xylulose (22), sodium diethyldithiocarbamate, L-methionine, and -propyl-di- -propylthiol-carbamate (163), 12 6-(substituted) purines (166), and two coumarin derivatives (164) have been found to promote Striga seed germination. None of these materials, however, appear to be constituents of the natural stimulant preparations. 

Catechol O-methyltransferase (COMT) is a widespread enzyme that catalyzes the transfer of the methyl group of S-adenosyl-l-methionine (AdoMet) to one of the phenolic group of the catechol substrate (Fig. 1). High COMT activity is found in the liver, kidney and gut wall... 

S-adenosyl-L-methionine (AdoMet, SAM) is a cofactor and the most important donor of the methyl (CH3-) group for methyltransferases, including COMT. When the methyl-group has been transferred, the remaining demethylated compound is called S-adenosyl-L-homo-cysteine. 

S-(5 -Deoxyadenosin-5 -yl)-L-methionine (AdoMet) S-[(1-Adenin-9-yl)-1,5-dideoxy-p-D-ribofuranos-5-yl]-L-methionine [trivial name S-adenosylmethionine (SAM)]... 

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