Methyltransferases, occurrence

Dervieux, T., Medard, Y., Verpillat, P., et al. (2001) Possible implication of thiopurine S-methyltransferase in occurrence of infectious episodes during maintenance therapy for childhood lymphoblastic leukemia with mercaptopurine. Leukemia. 15, 1706-1712. 

It should be noted, however, that these enzymes catalyzed single methylation steps, and did not accept partially methylated substrates for further O-methylation. The common occurrence of partially methylated flavonoids (16,17), such as those of C. americanum (Figure 1), raised the question as to whether multiple methyl transfers were catalyzed by one or several position-specific O-methyltransferases ... 

KAGAN, R. M., CLARKE, S., Widespread occurrence of 3 sequence motifs in diverse S- Adenosylmethionine-dependent methyltransferases suggests a common structure for these enzymes., Arch. Biochem. Biophys., 1994,310,417-427. 

Drotar A. G. A., Burton J., Tavernier J. E., and Eall R. (1987a) Widespread occurrence of bacterial thiol methyltransferases and the biogenic emission of methylated sulfur gases. Appl. Environ. Microbiol. S3, 1626-1644. 

Dervieux T, Medard Y, Baudouin V, Maisin A, Zhang D, Broly F, Loirat C, Jacqz-Aigrain E. lliiopurine methyltransferase activity and its relationship to the occurrence of rejection episodes in paediatric renal transplant recipients treated with azathioprine. Br J Clin Pharmacol 1999 48(6) 793-800. 

Some misinterpretations of the NBO performances still occur in the literature. For instance, 5-hydroxyguaiacyl (5-OH-G) units have been tentatively searched for among the NBO products recovered from transgenic tobacco plants deficient in caffeic acid 0-methyltransferase (COMT) activity [31], Studies on COMT-deficient bm3 maize line [32] have shown that the labile 5-OH-G units cannot survive NBO. This situation was anticipated in the pioneering studies of Kuc and Nelson [33], in which they suspected the occurrence of additional as yet undetected lignin units . By contrast and as explained in the next section, thioacidolysis provides an easy determination of 5-OH-G units in native or industrial lignins. 

It should be noted that methylation-linked repression of repair genes like that for 06-methylguanine-DNA-methyltransferase will impair DNA repair and will increase mutation rates. Furthermore, methylated CpG sequences are more prone to mutagenesis, because spontaneous deamination of 5-methyl-C will induce a C T transition. Gene silencing by hypermethylation may therefore favor the occurrence of mutational events during tumorigenesis. 

Martin, and A. Rodgman Effect of treatment of tobacco with ammonia or various ammonium salts on the levels of pyridines and pyrazines in smoke RDR, 1976, No. 3, January 29, see www.ijrtdocs.com 501003985 -4047. Mizusaki, S., Y. Tanabe, M. Noguchi, and E. Tamaki Phytochemical studies on tobacco alkaloids. XIV. The occurrence and properties of putrescine V-methyltransferase in tobacco roots Plant Cell Physiol. 12 (1971) 633-640. Mozayani, A. Phencychdine Effects on human performance and behavior, Eorensic Sd. Rev. 15 (2002) 61-73. Pailer, M. Chemistry of nicotine and related compounds (including biosynthetic aspects) in Tobacco alkaloids and related compounds, edited by U.S. Von Euler, MacMillan, New York, NY (1965) pp. 15-36. Pictet, A. and A. Rotschy Synthese des Nikotins [Synthesis of nicotine] Chem. Ber. 37 (1904) 1225-1235. 

Hepatitis 12 Histaminase 19, 20 Histamine human brain 60 kidney function, 74, 80 localization 4, 5 metabolism 17, 19 microcirculation 84 ff, 86 occurrence 49 ff pharmacology 70, 71 production 8 respiratory metabolism 89 turnover 23, 24 Histamine headache 126 Histamine-A-methyltransferase 17 Histidine decarboxylase 2, 7 Homoprotocatechuic acid see 3,4-Dihy-droxyphenylacetic acid Homovanillic acid see 3-Methoxy-4-hy-droxyphenylacetic acid 5-Hydroxindole acetic acid excretion 11, 12 microcirculation 86 occurrence 46 ff... 

Mizusaki S, Tanabe Y, Noguchi M, Tamaki E (1971) Phytochemical studies on tobacco alkaloids. XIV. Occurrence and properties of putrescine V-methyltransferase in tobacco roots. Plant Cell Physiol 12 633-640... 

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