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1

Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization.

100%

Szkopińska A.

|

2000

|

vol. 47

|

issue 2

469-480

EN

Ubiquinone, known as coenzyme Q, was shown to be the part of the metabolic pathways by Crane et al. in 1957. Its function as a component of the mitochondrial respiratory chain is well established. However, ubiquinone has recently attracted increasing attention with regard to its function, in the reduced form, as an antioxidant. In ubiquinone synthesis the para-hydroxybenzoate ring (which is the derivative of tyrosine or phenylalanine) is condensed with a hydrophobic polyisoprenoid side chain, whose length varies from 6 to 10 isoprene units depending on the organism. para-Hydroxybenzoate (PHB) polyprenyltransferase that catalyzes the condensation of PHB with polyprenyl diphosphate has a broad substrate specificity. Most of the genes encoding (all-E)-prenyltransferases which synthesize polyisoprenoid chains, have been cloned. Their structure is either homo- or heterodimeric. Genes that encode prenyltransferases catalysing the transfer of the isoprenoid chain to para-hydroxybenzoate were also cloned in bacteria and yeast. To form ubiquinone, prenylated PHB undergoes several modifications such as hydroxylations, O-methylations, methylations and decarboxylation. In eukaryotes ubiquinones were found in the inner mitochondrial membrane and in other membranes such as the endoplasmic reticulum, Golgi vesicles, lysosomes and peroxisomes. Still, the subcellular site of their biosynthesis remains unclear. Considering the diversity of functions of ubiquinones, and their multistep biosynthesis, identification of factors regulating their cellular level remains an elusive task.

2

Farnesyl diphosphate synthase; regulation of product specificity.

63%

Szkopińska A., Płochocka D.

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2005

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vol. 52

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issue 1

45-55

EN

Farnesyl diphosphate synthase (FPPS) is a key enzyme in isoprenoid biosynthesis which supplies sesquiterpene precursors for several classes of essential metabolites including sterols, dolichols, ubiquinones and carotenoids as well as substrates for farnesylation and geranylgeranylation of proteins. It catalyzes the sequential head-to-tail condensation of two molecules of isopentenyl diphosphate with dimethylallyl diphosphate. The enzyme is a homodimer of subunits, typically having two aspartate-rich motifs with two sets of substrate binding sites for an allylic diphosphate and isopentenyl diphosphate per homodimer. The synthase amino-acid residues at the 4th and 5th positions before the first aspartate rich motif mainly determine product specificity. Hypothetically, type I (eukaryotic) and type II (eubacterial) FPPSs evolved from archeal geranylgeranyl diphosphate synthase by substitutions in the chain length determination region. FPPS belongs to enzymes encoded by gene families. In plants this offers the possibility of differential regulation in response to environmental changes or to herbivore or pathogen attack.

3

Dolichols and enzymatic formation of dolichyl phosphate sugars in the thymus of mice on neoplastic transformation

51%

Szkopińska A., Palamarczyk G., Chojnacki T.

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vol. 32

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issue 1

63-70

4

Factors affecting oxygen-induced changes in the activity of CTP-dependent lipid kinases in yeast

50%

Szkopińska A.

Acta Biochimica Polonica

|

1990

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vol. 37

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issue 1

81-84

5

Subcellular compartmentation of dolichol taken up by mouse leukemia cells

45%

Jankowski W., Szkopińska A., Kula-Świeżewska E.

Acta Biochimica Polonica

|

1989

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vol. 36

|

issue 2

93-103

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Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization.

Farnesyl diphosphate synthase; regulation of product specificity.

Dolichols and enzymatic formation of dolichyl phosphate sugars in the thymus of mice on neoplastic transformation

Factors affecting oxygen-induced changes in the activity of CTP-dependent lipid kinases in yeast

Subcellular compartmentation of dolichol taken up by mouse leukemia cells