Lysine methylation system

In the case of the double NPS-protected lysine methyl ester, oxidation selectively takes place at the 6-sulfenamide function under spontaneous cyclization via the a-sulphe-namido group as nucleophile. Only one diastereoisomer of the A,A -bis(NPS)-protected methyl 6-amino-piperidine-2-yl-carboxylate seems to be formed. The transformation of a-amino alkanoates and diaryl or dialkyl disulfides to the aryl- or alkylsulfenimine derivatives can be performed electrochemically using MgBr2 as a mediator system. This reaction can either proceed in one step or starting from the corresponding sulfenamide [170]. 

Hayama et al.132 discussed the catalytic effects of silver ion-polyacrylic add systems toward the hydrolyses of 2,4-dinitrophenylvinylacetate 84 (DNPVA) by using the weak nudeophilicity of carboxylic groups and the change-transfer interactions between olefinie esters and silver ions133Metal complexes of basic polyelectrolytes are also stimulating as esterase models. Hatano etal. 34, 13S) reported that some copper(II)-poly-L-lysine complexes were active for the hydrolyses of amino acid esters, such as D- and L-phenylalanine methyl ester 85 (PAM). They... 

Morino and Snell32 ascribed the 420-nm species to a protonated internal pyridoxal-P-lysine aldimine and the 337-nm species to either a dipolar ionic form of the aldimine or to a substituted aldamine (an adduct at C-4 ). However, the dipolar ionic form absorbs at about 360 nm in aspartate transaminase and in the model systems containing Schiff bases of A-methylated PLP.34 It was suggested that the 337-nm species may be the enolimine tautomer.35,36 ... 

The results on the hydrolysis of partially methylated /3-casein by plasmin indicate that proteins radiomethylated to a low level can serve as substrates for trypsin-like enzymes and probably for proteinases in general. Because it is likely that methylation will interfere with enzymatic attack at lysine residues, the complete hydrolysis of /3-casein probably would not be possible. Studies on mastitic milk demonstrate the usefulness of 14C-methyl proteins for qualitative examination of protein hydrolysis in complex multiprotein systems where resolution and characterization of individual protein fragments is difficult. The requirements in such studies are the availability of pure samples of the proteins under investigation and a suitable technique for separating the radio-labeled protein from hydrolytic products. 

Thus, the lipid biosynthetic enzyme system evolved in extreme halophiles to utilize the (halophilic) mevalonate pathway for synthesis of virtually all of its hydrocarbon (isoprenoid/isopranoid) chains, rather than the (non-halophilic) fatty-acid synthetase system which was retained only for synthesis of normal fatty acid chains required for incorporation into proteins of the red membrane (Pugh and Kates, unpublished data). Starting from acetate and involving lysine, which provides the branch-methyl and methine carbons [88]), the mevalonate pathway proceeds to geranylgeranyl-PP (GG-PP) [13,15,89] as follows ... 

The fi-N-methyllysines are stable to acid hydrolysis and may be identified with the aid of an amino acid analyzer. With many routine analyzer systems e-N-monomethyl- and e-N-dimethyllysine elute as a shoulder or a partially resolved peak on the trailing edge of the lysine peak. If a 60 cm column is eluted with the buffer usually used for the 15 cm column these two methylated lysines are well resolved from lysine but not from each other. e-N-trimethyllysine usually elutes with lysine or slightly ahead of it in these systems (15 cm or 60 cm column eluted with pH 5.28 buffer). 

Benoiton et al. (1971) have found that lysine and s-N-monomethyl-lysine have similar 570/440 nm ratios after reaction with ninhydrin as measured with the analyzer, and that e-N-dimethyllysine and e-N-trimethyllysine also have similar 570/440 nm ratios, but the 570/440 nm ratios of the two pairs are different. This provided a method for estimating from the 570/440 nm ratio the content of e-N-monomethyl-lysine and e-N-dimethyllysine in hydrolysates that are analyzed in systems in which these two derivatives are not separated. For other analyzer systems that have been used to study methylated lysines, see the references cited above and also Deibler and Martenson (1973). 

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