On the biosynthesis of ubiquinones in plant mitochondria

Abstract

Isolated mitochondria from potato tubers, spinach leaves, and daffodil petals form intermediates of the ubiqujnone biosynthetic pathway (prenylated 4-hydroxybenzoate, prenylated phenols, and quinoid compounds) from [l -lSC]isopentenyl diphosphate and endogcnous or exogenous 4-hydroxybenzoate. In contrast [2-'4C]mevalonate 5-diphosphate, the immediate precursor of isopentenyl diphosphate was not accepted as a substrate. These results suggest that plant mitochondria have their own prenyltransferase and prenylation system, similar to the plastid compartment which also starts by the use of isopentenyl diphosphate [see Kreuz, K. and Kleinig, H. (1984) Eur. J. BiocArm. 141,

The Arabidopsis thaliana Type I Isopentenyl Diphosphate Isomerases Are Targeted to Multiple Subcellular Compartments and Have Overlapping Functions in Isoprenoid Biosynthesis

“…A mitochondria-specific isoform of IPP isomerase is not surprising given the previously reported role of mitochondria in the biosynthesis of some essential isoprenoids, such as ubiquinone (Lü tke-Brinkhaus et al, 1984), and the targeting of a specific isoform of FPP synthase to this compartment (Cunillera et al, 1997). While IPP has been shown to be taken up by mitochondria (Lü tke- Brinkhaus et al, 1984), if DMAPP cannot similarly be absorbed, then there would be an absolute requirement for an IPP isomerase in the mitochondrion to provide DMAPP for the construction of isoprenoids. Direct import of FPP into Sitosterol from wild-type and mutant plants gave virtually identical spectra (see Supplemental Figure 3 online).…”

“…For example, IPP import into mitochondria (Lü tke-Brinkhaus et al, 1984) and exchange of IPP between the cytosol and plastid have been documented by inhibitor studies in Arabidopsis (Laule et al, 2003) and in vivo feeding studies in several plant systems, including tobacco BY-2 cultures (Hemmerlin et al, 2003), snapdragon (Antirrhinum majus) (Dudareva et al, 2005), chamomile (Chamaemelum nobile) (Adam et al, 1999), and lima bean (Phaseolus lunatus) (Piel et al, 1998). In vitro studies with isolated membranes also support the transport of IPP from plastids to the cytosol (and possibly DMAPP, albeit at very low levels) (Bick and Lange, 2003) and from the cytosol to plastids (Kreuz and Kleinig, 1984;Soler et al, 1993;Flü gge and Gao, 2005).…”

Carotenoid biosynthesis in microorganisms and plants

“…Several types of this enzymes were isolated from carotenogenic and non-carotenogenic bacteria, fungi, plants and animal tissue, e. g. from tomato [78], Capsicum [79], Phycomyces [go], and Sinupis [Sl], as well as from yeast [82] and rat liver [83]. Some of these enzymes exhibit either affinities for several prenyl diphosphates or are monospecific for farnesyl diphosphate like the GGPP synthase from Phycomyces [80] and from rat [83]. In contrast, the enzymes from yeast [Xl] and from Methunobucterium thermoformicium [841 show no preference and convert the C, dimethylallyl diphospate (DMAPP), C,,, geranyl diphosphate (GPP), and C,, farnesyl diphosphate (FPP) equally well [82].…”

Molecular aspects of plastid envelope biochemistry

“…For instance, in vitro phytoene desaturation in chromoplast membranes employs molecular oxygen as the terminal acceptor, but quinone compounds were able to replace molecular oxygen [93]. In addition, phytoene synthase and desaturase [94] and zeaxanthine epoxidase [95] activities were demonstrated in envelope membranes from mature spinach chloroplasts. In cyanobacteria, a possible role for cytoplasmic membranes in carotenoid biosynthesis has not yet been investigated, although oxygen and NAD(P)+ dependence of phytoene desaturation have been demonstrated in vitro with Anacystis membranes [96].…”

“…The role of envelope quinones is not yet clear, but they could be involved in desaturation. For instance, phytoene desaturase which is probably present in chloroplast envelope membranes [94] uses molecular oxygen as the terminal electron acceptor, but quinone compounds are able to replace it in phytoene desaturation in Narcissus pseudonarcissus chromoplasts [93]. The participation of envelope quinones in fatty acid desaturation has not yet been demonstrated.…”