Carboxyl-0-methyltransferase dependence

Baron, R.A., Peterson, Y.K., Otto, J.C., Rudolph, J., and Casey, P.J. (2007). Time-dependent inhibition of isoprenylcysteine carboxyl methyltransferase by indole-based small molecules. Biochemistry 46 554-560. 

Fig. 22.7 Consensus effects of Spd and Spm on salicyclic acid metabolism and signaling cascade. Description is same as in legends to Fig. 22.1. GH3.5 GH3-like phytohormone amino acid synthetase, MeSA methyl salicylate, NPRl non-expressor of pathogenesis-related gene 1, NPR3 NPRl-like protein 3, NPR4 NPRl-like protein 4, SA sahcylic acid, SA-Asp Salicyloyl-L-aspartic acid, SAMT SAM-dependent carboxyl methyltransferase, TGA TGA transcription factor...

Phenazines — The phenazines are biosynthesized by the shikimic acid pathway, through the intermediate chorismic acid. The process was studied using different strains of Pseudomonas species, the major producers of phenazines. The best-known phenazine, pyocyanine, seems to be produced from the intermediate phenazine-1-carboxylic acid (PCA). Although intensive biochemical studies were done, not all the details and the intermediates of conversion of chorismic acid to PCA are known. In the first step, PCA is N-methylated by a SAM-dependent methyltransferase. The second step is a hydroxylative decarboxylation catalyzed by a flavoprotein monooxygenase dependent on NADH. PCA is also the precursor of phenazine-1-carboxamide and 1-hydroxyphenazine from Pseudomonas species. - - ... 

A second group of SAM-dependent methylases acts on much larger substrates, such as proteins and nucleic acids (9). Only recently has progress been made on isolating purified proteins which methylate macromolecules such as tRNA (10), mRNA (11), and proteins (12). In the case of tRNA (adenine-1)-methyltransferase (E.C. 2.1.1.36) (10a) and protein carboxyl-0-methyltransferase (E.C. 2.1.1.24) (13), kinetic studies are consistent with the random sequential reaction proposed for COMT, and thus suggest a direct methyl transfer in the ternary complex. One enzyme which does not show kinetics consistent with a direct methyl transfer is histamine-N-rnethyltransferase (E. C. 2.1.1.8) (14). The data reported are consistent with a double—displacement mechanism of... 

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