Cinnamate 4-monooxygenase

Thylakoid membranes containing phenylalanine ammonia-lyase and cinnamate 2-monooxygenase (D 22.2.1, D 22.2.2) Mitochondrial membranes containing benzoate synthetase system (D 22.2.5) Chalcone synthase (D 22.3.3)... 

Cinnamate 2-monooxygenase 2 glucosyltransferase 3 light-dependent isomerization 4 glu-cosidase 5 spontaneous cyclization 28 ... 

PHENYLALANINE AMMONIA-LYASE trans-CINNAMATE 4-MONOOXYGENASE CIRGADIAN RHYTHM CIRGE EFFEGT... 

The first step of flavonone biosynthesis begins with the deamination of the amino acid phenylalanine or tyrosine by a phenylalanine ammonia-lyase (PAL) or a tyrosine ammonia-lyase (TAL), which affords cinnamic acid and p-coumaric acid, respectively (Figure 6.36). The formed cinnamic acid is first hydroxylated to p-coumaric acid by a membrane-bound P450 monooxygenase, cinnamate 4-hydroxylase (C4H), and then activated to p-coumaroyl-CoA by a 4-coumarate-CoA ligase (4CL). 4CL catalyzes also the conversion of caffeic acid, feruhc acid, and cinnamic acid to caffeoyl-CoA, feruloyl-CoA, and cinnamoyl-CoA, respectively. 

In virus-inoculated tobacco, benzoic acid is converted by the monooxygenase enzyme, benzoic acid 2-hydroylase, into salicylic acid. NADPH was required. Feeding of phenylalanine, cinnamic acid, or o-coumaric acid (all potential precursors) failed to induce the enzyme (Leon et al., 1993). 

Cinnamic acid 4-hydroxyla a (EC 1.14.13.11) a mixed function monooxygenase, present in plants, which catalyses an early reaction in Flavonoid (see) biosynthesis, i.e. the insertion of an atom of oxygen into cinnamic acid to form 4-hydroxydnnamic acid (4-coumaric acid) with concomitant oxidation of one molecule of NADPH. The enzyme is a cytochrome P4S0 system associated with the microsom fraction, and is specific for the trans isomer of cinnamic acid. During the hydroxylation, hydrogen at position 4 (experimentally tritium in position 4) is retained, i.e. there is an NIH shift (see). In vitro, a thiol, e.g. 2-mercaptoethanol, is required for activity. (P.R.Rich C.J.Lamb Ear. J.Biochem. 72 (1977) 353-360)... 

Membranes of ER containing phenylalanine ammonia-lyase and cinnamate 4-monooxygenase (D 22.2.1)... 

Cinnamic acid derivatives Phenylalanine ammonia-lyase, cinnamate 2- and 4-monooxygenases (D 22.2.1, D 22.2.2) Phenol oxidase, 0-methyltransferases, cinnamic acid derivatives (D 22.2.1) M Un- known Inner membranes... 

Phenylalanine ammonia-lyase 2 cinnamate 4-monooxygenase 3 phenol oxidase 4 0-methyl-transferases, e.g., caffeate 0-methyltransferase... 

With the failure to demonstrate that norbelladine or its relatives plays a role in the biosynthesis of the mesembrine alkaloids, a reevaluation led to a modified approach in which attempts to identify the sequence of occurrence of the post-tyrosine and post-phenylalanine intermediates were made. There is now a substantial body of information available to suggest that phenylalanine and tyrosine have separate metabolic roles in plants belonging to the order Dictolyoden. Not only do they lack the enzyme phenylalanine hydroxylase (phenylalanine 4-monooxygenase) which is necessary for the conversion of phenylalanine to tyrosine, but the metabolic pathways of these two amino acids are generally quite different in secondary metabolism (70). Phenylalanine is involved in initial conversion to cinnamic acid and subsequent transformation to structural units of the so-called phenyl-propanoid pathway, which include Ar—C3, Ar—C2, and Ar—Cj structural entities. On the other hand, the role of tyrosine in the biosynthesis of secondary metabolities is most frequently seen as the precursor of Ar—Cj—N and Cg—C2—N units, and somewhat less frequently, as Ar—C2 and Q—C2 units. 

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