Synthesis of 4-carboxy-2-polyprenylphenols by a particulate fraction of baker's yeast

The preparation ofa cell-free homogenate and 10000 g particulate fraction with polyprenylpyrophosphate-p-hydroxybenzoate polyprenyltransferase activity from 0 to 7-day-old blocks of compressed baker's yeast is described. The synthesis of 4-carboxy-2-triprenylphenol from p-hydroxybenzoate and FPP by the particulate fraction has been studied in some detail. In particular it has been shown that the transferase catalysing the reaction is activated by Mg²⁺, has a pH optima of 7 and is inhibited by phosphate buffer. Intracellular distribution studies have established that in freshly grown cells of Saccharomyces carlsbergensis the greater part of the polyprenyl transferase activity is present in the mitochondria.     

Stimulation of rat liver 4-hydroxybenzoate: polyprenyl transferase activity by a cytosolic protein factor; evidence for a polyprenyl pyrophosphate transport protein

Rat liver postmicrosomal supernatant contains a factor which stimulates the 4-hydroxybenzoate:polyprenyl transferase activity of whole mitochondria and inner mitochondrial membrane fragments. The factor involved appears to be a heat stable, nondializable protein sensitive to tryptic hydrolysis and has been partially purified. Since this protein binds nonaprenyl pyrophosphate and stimulates its transport into mitochondria but shows no similar effect with 4-hydroxybenzoate, it is suggested that this protein also acts as an all trans polyprenyl pyrophosphate carrier protein.     

Synthesis of 3-polyprenyltoluquinols and 4-carboxy-2-polyprenylphenols by cell-free preparations of Euglena gracilis

Cell-free homogenates of Euglena gracilis are able to carry out the light- and Mg²⁺-independent syntheses of approximately equal amounts of a nonaprenyltoluquinol, an octaprenyltoluquinol and two uncharacterized compounds referred to as chromanols from homogentisate and a Micrococcus luteus extract that has been preincubated with isopentenylpyrophosphate (MLE-IPP). In addition they also synthesized substantial amounts (20%) of previously unencountered CHCl₃-soluble products from homogentisate and MLE-IPP, and the 2-deca-, 2-nona- (principal product) and 2-octa-prenyl forms of 4-carboxy-2-polyprenylphenol from p-hydroxybenzoate and MLE-IPP. The polyprenyltoluquinols were shown to be 3-polyprenyl-toluquinols, compounds postulated as intermediates on the pathway from homogentisate to plastoquinone, by determination of the ratio of ¹⁴C: ³H incorporated into them from 2,5-dihydroxyphenylacetic-[U-¹⁴C,4,6-³H₂] acid. Intracellular distribution studies using green, dark-grown and streptomycin-bleached cells, established that the 3-polyprenyltoluquinols are synthesized in the chloroplasts and the etioplasts, and that 4-carboxy-2-polyprenylphenols are synthesized in the mitochondria and a particle sedimenting at 1000–15000 g.