Disease relevance of ATC4H

• The CYP73A5 protein was expressed in insect cells using the baculovirus expression system and when reconstituted with lipid and NADPH-cytochrome P450 reductase resulted in C4H activity with a specific activity of 68 nmol min-1 nmol-1 P450 [1].
• Tyrosine ammonia lyase was substituted for phenylalanine ammonia lyase and cinnamate-4-hydroxylase in our E. coli clones and three different growth media were tested [2].

High impact information on ATC4H

• The increase in sinapate ester accumulation in the mutant is associated with an enhanced expression of the gene encoding cinnamate 4-hydroxylase, which appears to be the principal target of AtMYB4 and an effective rate limiting step in the synthesis of sinapate ester sunscreens [3].
• In contrast, it shares much less homology with cinnamate-4-hydroxylase, a P450 that catalyzes the hydroxylation of cinnamic acid three steps earlier in the general phenylpropanoid pathway [4].
• Biochemical characterization of the Arabidopsis ATR1/CYP73A5 and ATR2-1/CYP73A5 systems demonstrates that the two distantly related Arabidopsis reductases similarly support the first oxidative step of the phenylpropanoid general pathway [5].
• Of the three enzymes originally proposed to hydroxylate the 4-, 3-, and 5-positions of the aromatic ring, cinnamate 4-hydroxylase (C4H), which converts trans-cinnamic acid to p-coumaric acid, is the best characterized and is also the archetypal plant P450 monooxygenase [6].
• In transgenic Arabidopsis, the promoters of CYP98A3 and C4H showed wound inducibility and a comparable developmental regulation throughout the life cycle, except in seeds, where the CYP98A3 promoter construct was inactive while remaining active in silique walls [6].

Biological context of ATC4H

• The entire C4H coding sequence plus 2.9 kb of its promoter were isolated on a 5.4-kb HindIII fragment of this cosmid [7].
• A C4H promoter region of 907 bp contained all of the three cis-acting elements (boxes P, A, and L) conserved among the PAL and 4CL genes so far reported as controlling expression [1].
• To study the expression of this gene in Arabidopsis thaliana, a C4H cDNA clone from the Arabidopsis expressed sequence tag database was identified and used to isolate its corresponding genomic clone [7].
• The deduced amino acid sequence is 84.7% identical to that of mung bean C4H and therefore was designated CYP73A5 [1].
• A full-length cDNA encoding C4H was isolated from a hybrid poplar (Populus trichocarpa x P. deltoides) young leaf cDNA library [8].

Anatomical context of ATC4H

• Cinnamic acid 4-hydroxylase (C4H), a member of the cytochrome P450 monooxygenase superfamily, plays a central role in phenylpropanoid metabolism and lignin biosynthesis and possibly anchors a phenylpropanoid enzyme complex to the endoplasmic reticulum (ER) [8].
• Heterologous expression of CYP73A5, an Arabidopsis cytochrome P450 monooxygenase, in baculovirus-infected insect cells yields correctly configured P450 detectable by reduced CO spectral analysis in microsomes and cell lysates [9].

Associations of ATC4H with chemical compounds

• Immunoblot analysis showed that C4H was present in the microsomal fraction and microsomal preparations from strains expressing both enzymes efficiently converted cinnamic acid to p-coumaric acid with high specific activities [8].
• Yields of thioglycolic acid and Klason lignin in C4H-F5H lines were lower than in the wild-type, suggesting that F5H over-expression leads to a reduced deposition or an altered extractability of lignin in the transgenic plants [10].
• Besides its PAL activity, the recombinant PAL enzyme showed tyrosine ammonia lyase activity, which enabled the biosynthesis of naringenin without introducing cinnamate 4-hydroxylase (C4H) [11].
• For development of high-throughput P450 substrate profiling procedures, membrane proteins derived from cells overexpressing CYP73A5 and/or NADPH P450 reductase were incorporated into soluble His(6)-tagged nanoscale lipid bilayers (Nanodiscs) using a simple self-assembly process [9].
• CYP73A5 protein co-assembled with P450 reductase into Nanodiscs hydroxylates t-cinnamic acid using reduced pyridine nucleotide as an electron source [9].

Other interactions of ATC4H

• C4H (CYP73A5) expression was apparently coordinated in Arabidopsis with both PAL1 and 4CL in response to light and wounding [1].
• On the other hand, the C4H expression patterns exhibited no significant coordination with those of PAL2 and PAL3 [1].
• Although the light induction of CHS followed a time course similar to that observed with C4H, no induction of CHS was detected upon wounding [1].

Analytical, diagnostic and therapeutic context of ATC4H

• Southern blot analysis revealed that CYP73A5 is a single-copy gene in Arabidopsis [1].
• C4H expression was also strongly induced by elicitor-treatment in poplar cell cultures [8].

References