If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: phenyacetaldehyde biosynthesis, phenylacetaldehyde and phenylethanol biosynthesis
|Superclasses:||Biosynthesis → Aromatic Compounds Biosynthesis|
|Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis|
Plant volatiles contribute to aroma, flavor and scents of plants. [Pichersky06]. They are produced by the terminal branches of primary metabolic pathways. A single reaction and enzyme can convert a primary metabolite into a volatile compound. phenylacetaldehyde and 2-phenylethanol are two such aroma volatiles derived from phenylalanine [Tieman06]. Both compounds have pleasant fruity, floral smells and are major contributors of scent in many flowers. phenylacetaldehyde is the major scent volatile of hyacinth and lilac. 2-phenylethanol is the major aroma volatile associated with roses [Tieman07]. In tomato, both these compounds are a big impact on the fruit's flavor and the rapid interconversion of phenylacetaldehyde to 2-phenylethanol in vivo has been demonstrated [Tieman06]. They also act as powerful insect attractants and each attracts different sets of pollinating and predatory insects.
While the biosynthetic route of 2-phenylethanol production via 2-phenylethylamine and phenylacetaldehyde has experimental support [Tieman06] [Kaminaga06] [Sakai07] the proposed route via (E)-phenylacetaldehyde oxime so far lacks identified enzymes and genes in the Solanecea or other plants. However, a corresponding protein converting L-phenylalanine into (E)-phenylacetaldehyde oxime has been identified and characterized in Arabidopsis [Wittstock00] and the formation of (E)-phenylacetaldehyde oxime has also been reported in rose [Hayashi04a]. In addition the fast conversion of (Z)-phenylacetaldehyde oxime into 2-phenylethanol was observed in rose petals emphasizing the possible occurrence of this metabolic pathway in plants [Sakai07].
Despite the multiple roles these compounds play, little is known about their biosynthesis in plants. In yeast, 2-phenylethanol is produced from phenylalanine via phenylpyruvate and phenylacetaldehyde [Sakai07]. In petunia and tomato, the biosynthesis of 2-phenylethanol appears to have evolved into distinct pathways. The tomato enzymes catalyze the simple conversion of phenylalanine to 2-phenylethylamine, whereas the petunia enzyme is a complex one and catalyzes the efficient coupling of phenylalanine decarboxylation to oxidation, generating phenylacetaldehyde, ammonia, hydrogen peroxide and CO2 in stoichiometric amounts [Kaminaga06].
Hayashi04a: Hayashi S, Yagi K, Ishikawa T, Kawasaki M, Asai T, Picone C, Hiratake J, Sakata K, Takada M, Ogawa K, Watanabe N (2004). "Emission of 2-phenylethanol from its β-D-glucopyranoside and the biogenesis of these compounds from [2H8] L-phenylalanine n rose flowers." Tetrahedron 60: 7005-7013.
Kaminaga06: Kaminaga Y, Schnepp J, Peel G, Kish CM, Ben-Nissan G, Weiss D, Orlova I, Lavie O, Rhodes D, Wood K, Porterfield DM, Cooper AJ, Schloss JV, Pichersky E, Vainstein A, Dudareva N (2006). "Plant phenylacetaldehyde synthase is a bifunctional homotetrameric enzyme that catalyzes phenylalanine decarboxylation and oxidation." J Biol Chem 281(33);23357-66. PMID: 16766535
Sakai07: Sakai M, Hirata H, Sayama H, Sekiguchi K, Itano H, Asai T, Dohra H, Hara M, Watanabe N (2007). "Production of 2-phenylethanol in roses as the dominant floral scent compound from L-phenylalanine by two key enzymes, a PLP-dependent decarboxylase and a phenylacetaldehyde reductase." Biosci Biotechnol Biochem 71(10);2408-19. PMID: 17928708
Tieman06: Tieman D, Taylor M, Schauer N, Fernie AR, Hanson AD, Klee HJ (2006). "Tomato aromatic amino acid decarboxylases participate in synthesis of the flavor volatiles 2-phenylethanol and 2-phenylacetaldehyde." Proc Natl Acad Sci U S A 103(21);8287-92. PMID: 16698923
Tieman07: Tieman DM, Loucas HM, Kim JY, Clark DG, Klee HJ (2007). "Tomato phenylacetaldehyde reductases catalyze the last step in the synthesis of the aroma volatile 2-phenylethanol." Phytochemistry 68(21);2660-9. PMID: 17644147
Wittstock00: Wittstock U, Halkier BA (2000). "Cytochrome P450 CYP79A2 from Arabidopsis thaliana L. Catalyzes the conversion of L-phenylalanine to phenylacetaldoxime in the biosynthesis of benzylglucosinolate." J Biol Chem 275(19);14659-66. PMID: 10799553
Cooper92: Cooper RA, Knowles PF, Brown DE, McGuirl MA, Dooley DM (1992). "Evidence for copper and 3,4,6-trihydroxyphenylalanine quinone cofactors in an amine oxidase from the gram-negative bacterium Escherichia coli K-12." Biochem J 1992;288 ( Pt 2);337-40. PMID: 1334402
Roh94: Roh JH, Suzuki H, Azakami H, Yamashita M, Murooka Y, Kumagai H (1994). "Purification, characterization, and crystallization of monoamine oxidase from Escherichia coli K-12." Biosci Biotechnol Biochem 58(9);1652-6. PMID: 7765483
Shirota88: Shirota K, Fujisawa H (1988). "Purification and characterization of aromatic L-amino acid decarboxylase from rat kidney and monoclonal antibody to the enzyme." J Neurochem 51(2);426-34. PMID: 3392537
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