Methyltransferase applications

A common way to benefit from the ability to combine different molecular orbital methods in ONIOM is to combine a DFT or ab-initio description of the reactive region with a semi-empirical treatment of the immediate protein environment, including up to 1000 atoms. Due to the requirement for reliable semi-empirical parameters, as discussed in Section 2.2.1, this approach has primarily been used for non-metal or Zn-enzymes. Examples include human stromelysin-1 [83], carboxypeptidase [84], ribonucleotide reductase (substrate reaction) [85], farnesyl transferase [86] and cytosine deaminase [87], Combining two ab-initio methods of different accuracy is not common in biocatalysis applications, and one example from is an ONIOM (MP2 HF) study of catechol O-methyltransferase [88],... 

The process of oxidative deamination is the most important mechanism whereby all monoamines are inactivated (i.e. the catecholamines, 5-HT and the numerous trace amines such as phenylethylamine and tryptamine). Monoamine oxidase occurs in virtually all tissues, where it appears to be bound to the outer mitochondrial membrane. Whereas there are several specific and therapeutically useful monoamine oxidase inhibitors, inhibitors of catechol-O-methyltransferase have found little application. This is mainly due to the fact that at most only 10% of the monoamines released from the nerve terminal are catabolized by this enzyme. The main pathways involved in the catabolism of the catecholamines are shown in Figure 2.16. 

So far the major application of IVC has been to select enzymes. Griffiths has used IVC to select DNA methyltransferases and has successfully generated variants that can efficiently modify novel DNA target sequences [38]. This study provides a rare example of a laboratory-produced enzyme with a catalytic efficiency that surpasses that of the wild-type enzyme with the principle substrate. IVC has also... 

Lysine methyltransferases catalyze the transfer of methyl groups from the cosubstrate SAM to certain lysine residues in histone proteins. To characterize modulators of these transferases, the above-mentioned antibody-based assay protocols are also applicable. 

Lachman HM, Papolos DF, Saito T, Yu YM, Szumlanski CL, et al. 1996. Human catechol-O-methyltransferase pharmacogenetics Description of a functional polymorphism and its potential application to neuropsychiatric disorders 47. Pharmacogenetics 6 243-250. 

An extremely interesting application of KIEs and theory has been elucidating the effect of enzyme catalysis on the structure of the SN2 transition state. Schowen and coworkers29 30 measured the secondary a-deuterium and a-carbon 12C/13C KIEs for the enzyme-catalyzed SN2 methyl transfer reaction between G-adenosylmethionine (Fig. 18) and 3,4-dihydroxyacetophenone in the presence of the rat-liver enzyme catechol O-methyltransferase (COMT) at 37°C (Fig. 19) and for the closely related, uncatalyzed Sn2 reaction between methoxide ion and G-methyldibenzothiophenium ion in methanol at 25°C (Fig. 20). The near maximum a-carbon KIEs of 1.09 + 0.02 for the enzyme-catalyzed SN2 reaction and 1.08 + 0.01 for the uncatalyzed Sn2 reaction were taken as evidence that both transition states were symmetric. However,... 

The protein methylases which add methyl groups to lysine, arginine, and histidine residues of proteins may be too specific to have potential application in food protein modification. Protein O-methyltransferase appears to methylate the carboxyl groups of numerous proteins and could have broad enough specificity to be important for increasing the hydro-phobic properties of proteins through esterification of carboxyl groups. 

The biogenesis of the amino acids in position 2-11 in C. A proceeds through the usual biosynthetic routes with subsequent /V-methylation by 5-adenosylmethi-onine-dependent methyltransferases. The amino acid in position 1 is built up on the polyketide pathway and subsequently methylated at C-4. It has bron demonstrated that MeBmt is the starter of the non-ribo-somal peptide synthesis by means of a mutant strain of Tolypocladium inflatum Recent clinical data show, that C. application in transplantation medicine significantly increases the risk of cancer . 

Levac D, Murata J, Kim WS, De Luca V (2008) Application of carborundum abrasion fm investigating the leaf epidermis molecular cloning of Catharanthus roseus 16-hydroxyta-bersonine-16-O-methyltransferase. Plant J 53 225-236. doi 10.1111/J.1365-313X.2007.03337.X... 

Struck, A.-W., Thompson, M.L., Wong, L.S., and Micklefield, J. (2012) S-adenosyl-methionine-dependent methyltransferases highly versatile enzymes in biocatalysis, biosynthesis and other biotechnological applications. ChemBioChem, 13, 2642-2655. 

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