Publications

• Nonaprenyl-4-hydroxybenzoate transferase, an enzyme involved in ubiquinone biosynthesis, in the endoplasmic reticulum-Golgi system of rat liver.

  Kalen A., Appelkvist E.L., Chojnacki T., Dallner G.

  The properties and distribution of nonaprenyl-4-hydroxybenzoate transferase in rat liver were investigated with subcellular fractions, liver perfusion, and in vivo labeling with [3H]solanesyl-PP. In addition to some ubiquinone-9, only one labeled intermediate, i.e. nonaprenyl-4-hydroxybenzoate, wa ... >> More

  The properties and distribution of nonaprenyl-4-hydroxybenzoate transferase in rat liver were investigated with subcellular fractions, liver perfusion, and in vivo labeling with [3H]solanesyl-PP. In addition to some ubiquinone-9, only one labeled intermediate, i.e. nonaprenyl-4-hydroxybenzoate, was obtained. In the total microsomal fraction, the enzyme had a pH optimum of 7.5 and was completely inhibited by Triton X-100 and deoxycholate, but not by taurodeoxycholate and beta-octyl glucoside. Liver, kidney, and spleen demonstrated the highest activities of nonaprenyl-4-hydroxybenzoate transferase. Upon subcellular fractionation, high specific activities were found in smooth II microsomes and Golgi III vesicles. The enzyme was also found in lysosomes and plasma membranes, but only at low levels in rough and smooth I microsomes and mitochondria and not at all in peroxisomes and cytosol. When the product of the transferase reaction was used as a substrate in vitro and in a perfusion system, the only product obtained was end product ubiquinone-9. Although the transferase reaction was associated with the inner, luminal surface of microsomal vesicles, the terminal reaction(s) for ubiquinone-9 synthesis are found at the outer cytoplasmic surface. The results suggest that the major site for ubiquinone synthesis is the endoplasmic reticulum-Golgi system, which also participates in the distribution of ubiquinone-9 to other cellular membranes. << Less

  J Biol Chem 265:1158-1164(1990) [PubMed] [EuropePMC]

• Plastoquinone-9 biosynthesis in cyanobacteria differs from that in plants and involves a novel 4-hydroxybenzoate solanesyltransferase.

  Sadre R., Pfaff C., Buchkremer S.

  PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria diffe ... >> More

  PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria differs substantially from that in plants. We identified 4-hydroxybenzoate as being the aromatic precursor for PQ-9 in Synechocystis sp. PCC6803, and in the present paper we report on the role of the membrane-bound 4-hydroxybenzoate solanesyltransferase, Slr0926, in PQ-9 biosynthesis and on the properties of the enzyme. The catalytic activity of Slr0926 was demonstrated by in vivo labelling experiments in Synechocystis sp., complementation studies in an Escherichia coli mutant with a defect in ubiquinone biosynthesis, and in vitro assays using the recombinant as well as the native enzyme. Although Slr0926 was highly specific for the prenyl acceptor substrate 4-hydroxybenzoate, it displayed a broad specificity with regard to the prenyl donor substrate and used not only solanesyl diphosphate, but also a number of shorter-chain prenyl diphosphates. In combination with in silico data, our results indicate that Slr0926 evolved from bacterial 4-hydroxybenzoate prenyltransferases catalysing prenylation in the course of ubiquinone biosynthesis. << Less

  Biochem. J. 442:621-629(2012) [PubMed] [EuropePMC]