Bifunctional Polyphenol Oxidases: Novel Functions in Plant Pigment Biosynthesis

Strack, Dieter; Schliemann, Willibald

doi:10.1002/1521-3773(20011015)40:20<3791::aid-anie3791>3.0.co;2-t

Cited by 39 publications

(24 citation statements)

References 22 publications

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“…a PPO because AUS was classified as being a Cu 2+ containing PPO homologue. This is supported by the fact that the suggested reaction mechanism is actually based on an enzymatic o -quinone formation, which is a classical PPO reaction, followed by a non-enzymatic cyclization step [25]. The argument against is that the purified aureusidine synthase specifically acted on chalcones whereas 3,4-dihydroxyphenylalanine (DOPA), which is one of the most common substrates for PPOs, was not accepted [15].…”

Section: Discussionmentioning

confidence: 99%

4-Deoxyaurone Formation in Bidens ferulifolia (Jacq.) DC

et al. 2013

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The formation of 4-deoxyaurones, which serve as UV nectar guides in Bidens ferulifolia (Jacq.) DC., was established by combination of UV photography, mass spectrometry, and biochemical assays and the key step in aurone formation was studied. The yellow flowering ornamental plant accumulates deoxy type anthochlor pigments (6′-deoxychalcones and the corresponding 4-deoxyaurones) in the basal part of the flower surface whilst the apex contains only yellow carotenoids. For UV sensitive pollinating insects, this appears as a bicoloured floral pattern which can be visualized in situ by specific ammonia staining of the anthochlor pigments. The petal back side, in contrast, shows a faintly UV absorbing centre and UV absorbing rays along the otherwise UV reflecting petal apex. Matrix-free UV laser desorption/ionisation mass spectrometric imaging (LDI-MSI) indicated the presence of 9 anthochlors in the UV absorbing areas. The prevalent pigments were derivatives of okanin and maritimetin. Enzyme preparations from flowers, leaves, stems and roots of B. ferulifolia and from plants, which do not accumulate aurones e.g. Arabidopsis thaliana, were able to convert chalcones to aurones. Thus, aurone formation could be catalyzed by a widespread enzyme and seems to depend mainly on a specific biochemical background, which favours the formation of aurones at the expense of flavonoids. In contrast to 4-hydroxyaurone formation, hydroxylation and oxidative cyclization to the 4-deoxyaurones does not occur in one single step but is catalyzed by two separate enzymes, chalcone 3-hydroxylase and aurone synthase (catechol oxidase reaction). Aurone formation shows an optimum at pH 7.5 or above, which is another striking contrast to 4-hydroxyaurone formation in Antirrhinum majus L. This is the first example of a plant catechol oxidase type enzyme being involved in the flavonoid pathway and in an anabolic reaction in general.

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Section: Discussionmentioning

confidence: 99%

4-Deoxyaurone Formation in Bidens ferulifolia (Jacq.) DC

et al. 2013

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“…In support of this, in mutant four o'clock plant with yellow perianth, a transposition event in CYP76AD3, a homologue of CYP76AD1, alone was linked to red colouration that needs formation of cyclo-DOPA (Suzuki et al, 2014). However, it is difficult to draw a conclusive picture of enzymatic oxidation reactions in betalain biosynthesis as TYR and cytochrome P450 are localised in thylakoid and endoplasmic reticulum membranes (Strack and Schliemann, 2001;Tanaka, 2006), respectively, having DO activity, and along with them, perhaps, another PPO with DO activity also exists in soluble fraction. If this speculation is true, then how their regulation is achieved needs to be answered.…”

Section: Tyrosinasementioning

confidence: 99%

Plant betalains: Chemistry and biochemistry

2015

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“…Extensive studies on the biosynthetic reactions of betalains led to the discovery of several enzymes that function in early betalain biosynthesis: the polyphenol oxidase (PPO)-type tyrosinase (Steiner et al, 1996(Steiner et al, , 1999 and the extradiol DOPA dioxygenase (DOD). Tyrosinase is a copper-type bifunctional enzyme that catalyzes both hydroxylation of tyrosine to DOPA and the subsequent oxidation reaction that converts DOPA to o-quinone (Strack and Schliemann, 2001). The cyclisation of o-quinone to cyclo-DOPA is assumed to occur spontaneously (Strack et al, 2003).…”

Section: Biosynthesismentioning

confidence: 99%