Putative aminotransferase

PAL, phenylalanine ammonia lyase CA4H, cinnamic acid 4-hydroxylase CPR, Cytochrome P450 reductase 4CL, 4-coumaroyl-CoA ligase CA3H, coumaric add 3-hydroxylase COMT, caffeicacid O-methyltransferase SAM, S-adenosyl-methionine HCHL, hydroxycinnamoyl-CoA pAMT, putative aminotransferase AA, amino add KA, Keto add... 

Except the aminotransferase activity of AT-ACSlO and 12 isozymes, shown in heterologous nonplant systems, the catalytical status of a majority of members of AT-like enzymes is still unknown. The only exception is RH-ACS, whose expression has been evidenced to increase dramatically and correlate with ethylene levels in senescing petals of Rosa hyhrida Moreover, the investigation carried out by Barnes et on Pta-ACSl from conifers suggests the putative ACS activity of this isozyme. 

Formation of the Initial Cyclitol. The first steps of FOR production are the same as in the biosynthesis of STR in short, the first step in FOR biosynthesis is postulated to be the formation of a myo-inositol monophosphate (D-myo-inositol-3-phosphate or L-myo-inositol-1-phosphate) via the cellular l-myo-inositol-1-phosphate synthase as in the STR pathway (Ca pathway see Section 2.2.1.2). As in the itr-Att-clusters, no gene for this enzyme has been found in the/or-cluster. As a second step in FOR biosynthesis the dephosphorylation of D-myo-inositol-3-phosphate via an inositolmonophosphate phosphatase has to follow. A putative gene product with this activity is that of the ForA protein (cf. Tables 2.17 and 2.18). The cyclitol is postulated to be first converted via two enzymes, a cluster-encoded myo-inositol 3-dehydrogenase (ForG member of the GFO/IDH/MocA oxidoreductase family) and the L-glutamine icy//o-3-inosose 3-aminotransferase (ketocyclitol aminotransferase I ForS), to icy//o-inosamine (3-deoxy-3-amino- cy/to-mositol). 

Figure 3-5. Biosynthesis of salicylic acid. The enzymes involved in this pathway are (a) chorismate mutase (E.C. 5.4.99.5), (b) prephenate aminotransferase (E.C. 2.6.1.78 and E.C. 2.6.1.79), (c) arogenate dehydratase (E.C. 4.2.1.91), (d) phenylalanine ammonia lyase (E.C. 4.3.1.5), (e) presumed P-oxidation by a yet to be identified enzyme, (f) benzoic acid 2-hydroxylase, (g) isochorismate synthase (E. C. 5.4.4.2), and (h) a putative plant pyruvate lyase.

Tylosin contains a 16-membered lactone to which three deoxysugar moieties are attached. A disaccharide D-mycaminosyl-D-mycarose is linked at C5 and a D-mycinose at C23. Several genes have been cloned that encode deoxysugar biosynthetic enzymes most of them are involved in dTDP-D-mycaminose biosynthesis [48,49]. TylAl and TylA2 correspond to the dTDP-o-glucose synthase and dTDP-4,6-dehydratase, respectively. A putative isomerase not yet identified acts on dTDP-4-keto-6-deoxy-D-glucose, and then aminotransferase (TyiB) and C-methyltransferase (TylMl) to generate the final dTDP-D-mycaminose. 

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